CN L1-L8[1].pdf

Lecture 01 Introduction to Routers Module Code | Module Name | Lecture Title | Lecturer Module Delivery Per Week 2hr Lecture 1hr Tutorial 2hr Practical session ( once in 2 weeks) Module delivery clarifications Within the lecture, tutorial and lab sessions Panel of Lecturers Mr.Dhammika De Silva - Metro IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Module Assessment Criteria Continues Assessments – 40 % Online practical Exam 1 - 1 hr - ( week 5) – 10 % Online practical Exam 2 - 1 hr - ( week 12) – 10 % Mid Online - 1 hr - ( week 8) - 20 % Final Examination – 60% IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Recommended Books IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Lecture 1 Overview of Configuration of Network Devices IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Network Devices – Internal Components CPU Buses RAM ROM Flash Interfaces NVRAM Power Supply IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Cisco IOS Software As with a computer, a network device cannot function without an operating system. Cisco calls its OS as the Cisco Internetwork Operating System or Cisco IOS. IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Command Line Interface (CLI) The Cisco IOS software uses a command-line interface (CLI) as the traditional console environment. This environment is accessible through several connection methods: Console AUX port Telnet IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Dial-up Device Modem IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara User Level Passwords IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Router Modes IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Router Modes IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Router Modes IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Router Modes IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Router Memory IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Router Memory cont. RAM - Store running or active configuration file - Loses content when router is powered down - A working storage ROM - Read-Only Memory - Stores bootable IOS image and bootstrap program IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Router Memory cont. NVRAM - Provides storage for the startup configuration file - Retains content when router is powered down Flash memory - Holds the fully functional IOS image - Retains content when router is powered down - Is a type of electronically erasable, programmable ROM (EEPROM) IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Router Memory cont. Bootup program startup-config Bootable IOS running-config IOS IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Displaying configuration files show running-config show startup-config IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara Managing configuration files Copy Command - copy files in a router (configuration file, new version of the IOS Software) - Move configuration files among RAM, NVRAM, and TFTP server IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara copy running-config startup-config Router# copy startup-config running-config During bootup running-config startup-config Router# copy running-config startup-config Changes to the router are put in the running-config file. If the router loses power or reboots, everything in RAM is lost including the running-config file. To make sure the changes to the router’s configuration remain saved, you must copy the running-config from RAM into the startup-config into NVRAM: Router# copy running-config startup-config IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara copy running-config startup-config cont. Router#copy running-config startup-config Destination filename [startup-config]? Building configuration... Router#show startup-config ! version 12.0 service timestamps debug uptime The startup-config file now identical service timestamps log uptime no service password-encryption to running-config and the router will ! also have these changes if the router hostname Router ! reboots. ! ip subnet-zero ! interface Ethernet0 no ip address no ip directed-broadcast shutdown ! IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara running-config startup-config IOS copy tftp startup-config copy tftp running-config copy tftp flash copy flash tftp copy startup-config tftp copy running-config tftp IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara IT2050| Computer Networks | Introduction to Routers| Hansika Mahaadikara IT2050 - COMPUTER NETWORKS Lecture 2 IP Addressing IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Addressing with TCP/IP Address Physical Logical Port Address Address Address MAC Address IP Address Port Address Identify a Computer Identify a Process IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Physical Address Stored in the Network Interface Card (NIC) A hardware setting set by the manufacturer of NIC. Unchangeable Ex :- MAC address For Ethernet, the MAC address is a 48 bit or 12 Hex number Ex : 5A:B3:87:F1:93:7C 5A-B3-87-F1-93-7C MAC address operates in the Data Link Layer (Layer 2) Ethernet Frame CRC/FCS DATA DA SA SOF Preamble IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Logical Address Address scheme depends on the used protocol Widely used protocol is TCP/IP Ex :- IP Address 192.168.16.53 10.39.40.3 Logical address operates at the Network Layer (Layer 3) IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara IP Address Uniquely identifies devices IP Version 4 (IPV4) 32 bit scheme IP Addresses IP Version 6 (IPV6) (IPng) 128 bit scheme IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara IP Version 4 (IPV4) The 32 bits are represented in following manner. Byte 1. Byte 2. Byte 3. Byte 4 ( 1 byte = 8 bits) IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara IP Version 4 (IPV4) cont. IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara IP Version 4 (IPV4) cont. The minimum value of a byte 00000000 = 0 The maximum value of a byte 11111111 = 255 The minimum IP Address 0.0.0.0 The maximum IP Address 255.255.255.255 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Network ID and Host ID IP Addresses  Network ID + Host ID Class Net ID Host ID A 1 Byte 3 Bytes B 2 Bytes 2 Bytes C 3 Bytes 1 Byte IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara IPv4 Address Classes 10 Rick Graziani [email protected] IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Classes of IP addresses cont. Class D is introduced for Multicasting Class E is reserved IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Classes of IP addresses cont. Class D Addresses A Class D address begins with binary 1110 in the first octet. First octet range 224 to 239. Class D address can be used to represent a group of hosts called a host group, or multicast group. Class E Addresses First octet of an IP address begins with 1111 Class E addresses are reserved for experimental purposes and should not be used for addressing hosts or multicast groups. IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Class A byte 1 0 Class B byte 1 1 0 Class C byte 1 1 1 0 Class Minimum Network ID Maximum Networks ID 0 0000000 0 1111111 A 0 127 10 000000.00000000 10 111111.11111111 B 128.0 191.255 C 110 00000.00000000.00000000 110 11111.11111111.11111111 192.0.0 223.255.255 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Class A – 2^7 Class B – 2^14 Class C – 2^21 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Network Address and Broadcast Address For the Network Address, the Host ID part of the IP Address will be considered as All 0s For the Broadcast Address, the Host ID part of the IP Address will be considered as All 1 Ex : 103.58.35.1 This is a Class A address Net ID is = 103 Host ID is = 58.35.1 Network Address  103.0.0.0 Broadcast Address  103.255.255.255 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara 198. 8. 0. 1 Class C 1100 0110. 0000 1000. 0000 0000. 0000 0001 Network ID : 3 bytes (24 bits) Host ID : 1 byte (8 bits) Both in Network ID and Host ID all 0s and all 1s are reserved for special purposes. The actual maximum no. of Hosts per Network =28 - 2 = 254 Network Address : 1100 0110. 0000 1000. 0000 0000. 0000 0000 (198.8.0.0) Broadcast Address : 1100 0110. 0000 1000. 0000 0000. 1111 1111 (198.8.0.255) IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Classful Addressing - Subnet Mask Net ID part : All 1’s Host ID part : All 0’s IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Exercise IP Address Class Subnet Actual Network Broadcast Mask No.of Address Address hosts 140.35.45.55 50.60.70.5 201.35.40.201 125.38.55.185 193.201.55.105 127.53.35.10 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara IP address of a Router A router has many ports. (LAN and WAN Ports) An IP address is assigned to each port. IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Default Gateway IP Address Network Address Gateway IP Address 120.0.0.0 120.0.0.50 152.20.0.0 152.20.0.50 200.53.30.0 200.53.30.50 201.55.30.0 201.55.30.50 138.57.0.0 138.57.0.50 180.50.0.0 180.50.0.50 The IP address of router port which is connected to a particular LAN is called the “Gateway IP Address” of the LAN IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Public IP Addresses A public IP address is any valid address that can be accessed over the Internet The Internet is a Public Computer Network which is spread all over the world. Allocations of IP addresses are controlled by the Internet Assigned Number Authority (IANA) which responsible for the IP address ranges allocation to different countries. CINTEC assigns different range of IP address to different Internet Service Providers (ISPs) The ISPs allocate IP addresses to their customers Sri Lanka Telecom(SLT) provides allocates 8 IP addresses for each 64 kb/s leased line. IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Private IP Addresses A private IP address is address assigned to a device on a private LAN that is accessible only within the LAN. A network which is not connected to Internet can use any IP address range without obtaining any permission It is not advisable to use any IP address since the network may connect to Internet in the future To avoid such problems, IANA has reserved some IP address ranges for private use Class Private Network Address No.of Networks A 10.0.0.0 1 B 172.16.0.0 to 172.31.0.0 16 C 192.168.0.0 to 192.168.255.0 256 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara IP special addresses Net ID Host ID Remarks Network Address Specific All 0’s None Direct Broadcast Specific All 1’s Destination Address Address Limited Broadcast All 1’s All 1’s Destination Address Address This Host on this All 0’s All 0’s Source Address Network Specific host on this All 0’s Specific Destination Address network Loopback Address 127 Any Destination Address IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Network Address IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Direct Broadcast Address IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Limited Broadcast Address IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara This host on this network IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Specific host on this network IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Loopback address IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Classful Addressing IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Masking Concept IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara AND Operation IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Subnetting – Classless Addressing Suppose you are given a network address 150.100.0.0 /16 for your network. 10010110.01100100.00000000.00000000 You have the computers of Finance, Production and Administration Sections. In order to enhance the efficiency of network you want divide this into three networks. But you cannot get another two network addresses. This requirement can be satisfied from the same network address by using the subnet concept. Now the IP address is divided into three parts. Net ID Subnet ID Host ID IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Classless Addressing cont. The original Net ID bits not changed. Part of Host ID is allocated for “Subnet ID”. Most significant bits allocated as Subnet ID. XXXX XXXX. XXXX XXXX.. XXXX XXXX. XXXX XXXX Net ID Subnet ID Host ID IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Classless Addressing cont. subnets can be written as Subnet 0 10010110.01100100.00000000.00000000 Subnet 1 10010110.01100100.01000000.00000000 Subnet 2 10010110.01100100.10000000.00000000 Subnet 3 10010110.01100100.11000000.00000000 In dotted decimal, it can be written as, Subnet 0 address 150.100.0.0 /18 Subnet 1 address 150.100.64.0 /18 Subnet 2 address 150.100.128.0 /18 Subnet 3 address 150.100.192.0 /18 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Classless Addressing cont. For the above example the Finance, Production and Administration Sections can be put to three subnets as follows. Consider the hosts in subnet 150.100.64.0 150.100.64.0 The IP addresses can be given as 150.100.64.1 R 150.100.64.2 150.100.128.0 150.100.64.3 150.100.64.4 etc. 150.100.192.0 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Classless Addressing cont. In classless addressing the number of bits for network address cannot be decided. Indicated with a “/” symbol. The IP address is written as, 150.100.64.1 /18 150.100.64.2 /18 150.100.64.3 /18 the subnet mask will be, 11111111.11111111.11000000.00000000 255.255.192.0 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Write the possible 12 subnet addresses of 150.72.0.0 / 16 network. 150.72.96.0 / 20 150.72.0.0 / 20 150.72.16.0 / 20 150.72.112.0 / 20 150.72.32.0 / 20 150.72.128.0 / 20 150.72.48.0 / 20 150.72.144.0 / 20 150.72.64.0 / 20 150.72.160.0 / 20 150.72.80.0 / 20 150.72.176.0 / 20 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara VLSM Variable Length Sub-netting IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara An organization is granted the block 130.34.12.64/26. The organization needs 4 subnets. What is the subnet prefix length? Solution We need 4 subnets, which means we need to add two more bits (log2 4 = 2) to the site prefix. The subnet prefix is then /28. 40 TCP/IP Protocol Suite IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara VLSM Variable Length subnet Masking The number of devices are not equal in all the subnets Prefixes vary for separate subnets IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Class-full routing – Only allows for one subnet mask for all networks VLSM & Classless routing – The process of subnetting a subnet – More than one subnet mask can be used – More efficient use of IP addresses as compared to classfull IP addressing IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara An organization is granted a block of addresses with the beginning address 14.24.74.0/24. There are 232−24= 256 addresses in this block. The organization needs to have 11 subnets as shown below: a. 2 subnets, each with 64 addresses. b. 2 subnets, each with 32 addresses. c. 3 subnets, each with 16 addresses. d. 4 subnets, each with 4 addresses. Design the subnets. 44 TCP/IP Protocol Suite IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara TCP/IP Protocol Suite 45 IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara VLSM Example using /30 subnets 207.21.24.0/24 network subnetted into eight /27 (255.255.255.224) subnets This network has seven /27 subnets with 30 hosts each AND eight /30 subnets with 2 hosts each. /30 subnets are very useful for serial networks. 207.21.24.192/27 subnet, subnetted into eight /30 (255.255.255.252) subnets IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara 207.21.24.192/27 207.21.24. 11000000 /30 Hosts Bcast 2 Hosts 0 207.21.24.192/30 207.21.24. 110 00000 01 10 11.193 &.194 1 207.21.24.196/30 207.21.24. 110 00100 01 10 11.197 &.198 2 207.21.24.200/30 207.21.24. 110 01000 01 10 11.201 &.202 3 207.21.24.204/30 207.21.24. 110 01100 01 10 11.205 &.206 4 207.21.24.208/30 207.21.24. 110 10000 01 10 11.209 &.210 5 207.21.24.212/30 207.21.24. 110 10100 01 10 11.213 &.214 6 207.21.24.216/30 207.21.24. 110 11000 01 10 11.217 &.218 7 207.21.24.220/30 207.21.24. 110 11100 01 10 11.221 &.222 Rick Graziani 47 [email protected] IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara 207.21.24.192/30 207.21.24.192/30 207.21.24.204/30 207.21.24.204/30 207.21.24.216/30 207.21.24.216/30 207.21.24.96/27 207.21.24.128/27 207.21.24.64/27 207.21.24.64/27 207.21.24.208/30 207.21.24.196/30 207.21.24.196/30 207.21.24.200/30 207.21.24.212/30 207.21.24.160/27 207.21.24.224/27 207.21.24.32/27 207.21.24.0/27 207.21.24.160/27 207.21.24.224/27 This network has seven /27 subnets with 30 hosts each AND seven /30 subnets with 2 hosts each (one left over). /30 subnets with 2 hosts per subnet do not waste host addresses on serial networks. IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara VLSM and the Routing Table Routing Table without VLSM RouterX#show ip route Displays one subnet mask for 207.21.24.0/27 is subnetted, 4 subnets all child routes. Classful C 207.21.24.192 is directly connected, Serial0 mask is assumed for the C 207.21.24.196 is directly connected, Serial1 parent route. C 207.21.24.200 is directly connected, Serial2 C 207.21.24.204 is directly connected, FastEthernet0 Each child routes displays its own subnet mask. Classful mask is included for the parent route. Routing Table with VLSM RouterX#show ip route 207.21.24.0/24 is variably subnetted, 4 subnets, 2 masks C 207.21.24.192 /30 is directly connected, Serial0 C 207.21.24.196 /30 is directly connected, Serial1 C 207.21.24.200 /30 is directly connected, Serial2 C 207.21.24.96 /27 is directly connected, FastEthernet0 Parent Route shows classful mask instead of subnet mask of the child routes. Each Child Routes includes its subnet mask. IT 2050| Computer Networks| IP addressing| Hansika Mahaadikara Computer Networks Lecture 3 IPv6 Addressing Why IPv6  IPv4 has a theoretical maximum of 4.3 billion addresses  plus private addresses in combination with NAT  NAT having limitations in peer-to-peer communications  With an Internet of things, devices other than computers, tablets, and smartphones, sensors, Internet-ready devices, automobiles, biomedical devices, household appliances, natural ecosystems etc… need to connect to the internet. Why IPv6 How it looks like  IPv6 has a larger 128-bit address space  340 undecillion addresses. (That is the number 340, followed by 36 zeroes.)  When the IETF began its development of a successor to IPv4, so it fix the limitations of IPv4 and include additional enhancements  Ex- 2001:0DB8:0000:1111:0000:0000:0000:0200 Hextet used to refer to a segment of 16 bits or four hexadecimals IPv4 and IPv6 Coexistence  Dual Stack –dual stack allows IPv4 and IPv6 to coexist on the same network segment. Dual stack devices run both IPv4 and IPv6 protocol stacks simultaneously.  Tunneling –tunneling is a method of transporting an IPv6 packet over an IPv4 network. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data.  Translation – Network Address Translation 64 (NAT64) allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 packet is translated to an IPv4 packet and vice versa. Address formats IPv6 Address - Rule 1 (Omitting Leading 0s)  The first rule to help reduce the notation of IPv6 addresses is any leading 0s (zeros) in any 16-bit section or hextet can be omitted  01AB can be represented as 1AB  09F0 can be represented as 9F0  0A00 can be represented as A00  00AB can be represented as AB IPv6 Address -Rule 2 (Omitting All 0 Segments)  A double colon (::) can replace any single, contiguous string of one or more 16-bit segments (hextets) consisting of all 0’s  Double colon (::) can only be used once within an address otherwise the address will be ambiguous  Known as the compressed format  2001:0DB8::ABCD:0000:0000:1234  2001:0DB8::ABCD:0000:0000:0000:1234  2001:0DB8:0000:ABCD::1234  2001:0DB8:0000:0000:ABCD::1234 IPv6 Address Types  There are three types of IPv6 addresses:  Unicast  Multicast  Anycast *** IPv6 does not have broadcast addresses. IPv6 Unicast Addresses  Global unicast  Similar to a public IPv4 address.  Globally unique, Internet routable addresses.  Global unicast addresses can be configured statically or assigned dynamically.  Currently, only global unicast addresses with the first three bits of 001 or 2000::/3 are being assigned. (The first hextet has a range of (2000) to (3FFF).  Link-local  Link-local addresses are used to communicate with other devices on the same local link. (The first hextet has a range of (FE80) to (FEBF).)  Unique local  Similar to the private addresses for IPv4, but there are significant differences.  (FC00::/7 to FDFF::/7) *** 2001:0DB8::/32 address has been reserved for documentation purposes Host Configuration  Manually configuring the IPv6 address on a host is similar to configuring an IPv4 address.  the default gateway address configured for PC1 is 2001:DB8:ACAD:1::1. This is the global unicast address of the Router GigabitEthernet interface on the same network.  the default gateway address can be configured to match the link-local address of the GigabitEthernet interface of the router. Dynamic Configuration - SLAAC  Stateless Address Autoconfiguration (SLAAC) is a method that allows a device to obtain its prefix, prefix length, default gateway address, and other information from an IPv6 router without the use of a DHCPv6 server. EUI-64 Process  IEEE defined the Extended Unique Identifier (EUI) or modified EUI-64 process. This process uses a client’s 48-bit Ethernet MAC address, and inserts another 16 bits in the middle of the 48-bit MAC address to create a 64-bit Interface ID.  Step 1: Divide the MAC address between the OUI and device identifier.  Step 2: Insert the hexadecimal value FFFE, which in binary is: 1111 1111 1111 1110  Step 3: Convert the first 2 hexadecimal values of the OUI to binary and flip the U/L bit (bit 7). In this example, the 0 in bit 7 is changed to a 1 Questions ? IT2050 - Computer Networks Lecture 3 Routing Protocols Ms. Hansika Mahaadikara IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara What Is Routing? To route, a router needs to do the following: – Know the destination address. – Identify the sources it can learn from. – Discover possible routes. – Select the best route. – Maintain and verify routing information. 10.120.2.0 172.16.1.0 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara What Is Routing? (cont.) 10.120.2.0 172.16.1.0 E0 S0 Network Destination Exit Protocol Network Interface Connected 10.120.2.0 E0 Routed Protocol: IP Learned 172.16.1.0 S0 Routers must learn destinations that are not directly connected. IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Identifying Static & Dynamic Routes Static Route Dynamic Route Uses a route that a network Uses a route that a network routing administrator enters into the protocol adjusts automatically for router manually topology or traffic changes IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Direct Delivery Send a message to a machine in the SAME LAN IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Indirect Delivery IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Indirect Delivery cont. To send a packet from source to destination, need to go to the network ( packet should go from router to router ) All routers should maintain a routing table IP packet is analyzed at the router and correct path is selected form the routing table The packet is sent though that path Indirect delivery is done using the routing strategies IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Routing Table IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Adaptive Routing Routing Strategies There are four routing strategies - Fixed Routing - Flooding - Random Routing - IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Adaptive Routing Each router maintains a routing table Routing table modifies itself according to the network changes Advantages - Network traffic is minimized - Low latency - The best route will be selected most Disadvantages - Router memory need to keep a routing table IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Routing Methods used in Adaptive Routing Next hop routing Host specific Network specific Default routing IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Host Specific Routing Each router keeps one record/entry for each Table entry has Host IP and the Interface Host Address Interface 192.168.50.1 E0 192.168.50.6 E0 172.18.2.9 S1 172.18.5.96 S1 Disadvantages Large number of records Table updating is difficult and complex as it should be done for each and every host (if the host IP changes) IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Network Specific Routing Each router keeps a table entry for each network (one record for one network) Table entry has Network address and Interface Network Address Interface 192.168.50.0 E0 172.18.0.0 S1 Advantages Number of records are limited (Table updates are not for each host but for a network) Update is easy IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Routing Table update Methods Basic methods to update routing tables - Connected - Static - Dynamic IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Connected Once the router is connected to the network its interfaces are given IP addresses With that router automatically identifies the network addresses to which it connected IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Connected cont. R1#show ip route Codes: C - connected, S - static, Gateway of last resort is not set 172.16.0.0/24 is subnetted, 2 subnets C 172.16.2.0 is directly connected, Serial0/0/0 C 172.16.3.0 is directly connected, FastEthernet0/0 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Static Administrator can manually give routing table records Router(config)#ip route IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Static cont. R1(config)# R1(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.2 R1(config)#ip route 192.168.1.0 255.255.255.0 172.16.2.2 R1(config)#ip route 192.168.2.0 255.255.255.0 172.16.2.2 R1(config)# R1#show ip route Codes: C - connected, S - static Gateway of last resort is not set 172.16.0.0/24 is subnetted, 3 subnets S 172.16.1.0 [1/0] via 172.16.2.2 C 172.16.2.0 is directly connected, Serial0/0/0 C 172.16.3.0 is directly connected, FastEthernet0/0 S 192.168.1.0/24 [1/0] via 172.16.2.2 S 192.168.2.0/24 [1/0] via 172.16.2.2 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Static cont. Advantages: Minimal CPU processing Easier for administrator to understand and configure Disadvantages: Configuration and maintenance is time-consuming Configuration is error-prone Administrator should maintain changing route information Does not scale well with growing networks; maintenance becomes complex Requires complete knowledge of the whole network for proper implementation IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Default Routing Last record in the routing table Indicates the route/path to be taken, if any of the records does not match with the IP packet destination IP address Stub networks only use default routing , Stub networks have only one exit port out of the network R(config)#ip route 0.0.0.0 0.0.0.0 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Default Routing cont. B(config)# B(config)#ip route 0.0.0.0 0.0.0.0 172.16.2.2 B(config)# B#show ip route Codes: C - connected, S - static Gateway of last resort is 172.16.2.2 to network 0.0.0.0 172.16.0.0/24 is subnetted, 2 subnets C 172.16.1.0 is directly connected, FastEthernet0/0 C 172.16.2.0 is directly connected, Serial2/0 S* 0.0.0.0/0 [1/0] via 172.16.2.2 B# IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Dynamic Routing Scenario IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Dynamic Routing Scenario IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Dynamic Routing tables are updated automatically by using routing protocols Routing tables have Initially only connected records Then add static’ records Then automatic dynamic updates IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Dynamic cont. Advantages: Administrator has less work maintaining the configuration when adding or deleting networks Protocols automatically update, according to the topology changes. Configuration is less error-prone Suitable for More scalable, growing networks Disadvantages: Router resources are used (CPU cycles, memory and bandwidth) More administrator knowledge is required for configuration, verification, and troubleshooting IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Routing Protocols IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Features of Routing Protocols Network changes (addition or removal or fault) are automatically updated in routing tables of all routers When there are many routes to a destination, the best route should be selected Share the traffic through different routes IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara What Is a Routing Protocol? Routing Protocols 10.120.2.0 172.16.1.0 allow routers to E0 S0 dynamically advertise and learn routes, determine which routes are available and which are the Network Protocol Destination Network Exit Interface 172.17.3.0 most efficient routes Connected 10.120.2.0 E0 to a destination RIP 172.16.2.0 S0 EIGRP 172.17.3.0 S1 Routing Protocol: RIP, EIGRP,OSPF IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Routing Protocols IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Routing Protocols cont. An autonomous system (AS) is a collection of routers under a common administration ex : a company's internal network Interior Gateway Protocols (IGP) are used for intra-autonomous system routing (routing inside an autonomous system) Exterior Gateway Protocols (EGP) are used for inter-autonomous system routing (routing between autonomous systems) IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Routing Protocols cont. IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Interior Gateway Protocols (IGP) IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara RIP (Routing Information Protocol) IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara RIP (Routing Information Protocol) A Distance-vector routing protocol It sends the complete routing table out to all active interfaces in every 30 seconds Only uses hop count to select best way to a remote network RIP works well in small networks, but it is inefficient on large networks There are two versions RIP v1, RIP v2 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara RIP Configuration Router(config)#router rip Router(config-router)#network < network-address> Directly connected network addresses IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara RIP Configuration Example Version 1 E0 S0 S1 S0 S1 E0 172.16.0.0 A 192.168.1.0 B C 172.16.0.1 10.0.0.1 10.0.0.2 11.0.0.1 11.0.0.2 192.168.1.1 router rip 2.3.0.0 router rip 2.3.0.0 network 172.16.0.0 network 192.168.1.0 network 10.0.0.0 network 11.0.0.0 router rip network 10.0.0.0 Network 11.0.0.0 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Configure RIP V2 Classless Sub-networks Router(config)#router rip Router(config)#version 2 Router(config-router)#network < network-address> : Directly connected sub-network addresses IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara RIP Configuration Example Version 2 E0 S0 S1 S0 S1 E0 172.16.64.0 A 192.168.1.128 B C 172.16.64.1 10.0.1.1 10.0.1.2 10.0.2.1 10.0.2.2 192.168.1.129 router rip router rip Version 2 Version 2 No auto-summary No auto-summary network 172.16.64.0 network 192.168.1.0 network 10.0.1.0 network 10.0.2.0 router rip Version 2 No auto-summary network 10.0.1.0 Network 10.0.2.0 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Displaying the IP Routing Table 10.0.1.2 E0 S0 S1 S0 S1 E0 172.16.64.0 A 192.168.1.128 B C 10.0.1.0 10.0.2.0 RouterA#sh ip route Codes: C - connected, S - static, I - IGRP, R – RIP 172.16.0.0/16 is subnetted, 1 subnets C 172.16.64.0 is directly connected, Ethernet0 10.0.0.0/8 is subnetted, 2 subnets R 10.0.2.0/24 [120/1] via 10.0.1.2, 00:00:07, Serial0 C 10.0.1.0/24 is directly connected, Serial0 R 192.168.1.128/26 [120/2] via 10.0.1.2, 00:00:07, Serial2 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara RIP Timers Periodic Timer - A timer kept at each router for sending its routing table information to its neighbors in every 30 seconds. Expiration Timer - If a router does not get the updates from a neighboring router for a long time ,( means it is a problem with the neighboring router) the main router removes the updates got from that neighboring router - Is called expiration time ( 180 seconds ) IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Problems with RIP Slow Convergence Routing tables are sent to neighbors every 30 seconds When there are large number of routers in the network ,it will take some time to get all the details to each and every router.There is a delay in getting an updated routing table. Solution Triggered updates Information that needed to be updated immediately is informed to the other routers without waiting for the periodic time. IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Counting to infinity Solution - Route Poisoning When a network goes down the router that is connected to that network will get that information first So that router updates its table saying this network is down (unreachable ) In the routing table it says number of hops for that particular network as infinity (or in RIP as 16) IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Instability Once a router (P) get some updates from other router (Q) router P will updates it routing table and new routing table sent again to previous router. With time this will lead to having wrong updated tables in the routers and ultimately to an unstable situation Solution Spilt Horizon - Do not send same information via the link which that information came from IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Solutions Split Horizon When the router sends routing table information to the neighbors, it will not send the information that it got from that particular router So the routing table information will be selected and send IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Hold down Timer Once a network goes down, that information will be immediately sent to the other routers Because of the network connections there is a possibility to get some wrong information about that particular network from other routers Therefore once a network down information is received, the router will start the hold down timer, during which time any updates regarding that particular network is ignored. IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Poison Reverse In general split horizon will apply for information passing But the split horizon will not be applied in the case of the information like network is down IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara IGRP AD - 100 (Interior Gateway Routing Protocol ) A cisco proprietary distance-vector routing protocol Maximum hop count is 255 Used in large networks EIGRP is the enhanced version of IGRP IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara EIGRP IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara EIGRP (Extended Interior Gateway Routing Protocol ) IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara Features EIGRP was initially released in 1992 as a proprietary protocol available only on Cisco devices. In 2013, Cisco released a basic functionality of EIGRP as an open standard to the IETF as an informational RFC. Other networking vendors can now implement EIGRP on their equipment to interoperate with both Cisco and non-Cisco routers running EIGRP. IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara EIGRP Metric AD - 90 A ‘ Composite metric ‘ is used EIGRP uses bandwidth and delay of the line by default as a metric for determining the best route to an internetwork Metric is a combination of bandwidth, delay of the line , Reliability, load and Maximum Transmission Unit (MTU) Reliability, load, and Maximum Transmission Unit (MTU) are not used by default IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara EIGRP metric values Bandwidth - The slowest bandwidth among all of the outgoing interfaces, along the path from source to destination. Delay - The cumulative (sum) of all interface delay along the path (in microseconds). IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara EIGRP Configuration Router(config)#router Eigrp Router(config-router)#network < network address > : Directly connected network addresses < AS number > : Autonomous Systems Number IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara EIGRP Configuration Example E0 S0 S1 S0 S1 E0 172.16.64.0 A 192.168.1.128 B C 172.16.64.1 10.0.1.1 10.0.1.2 10.0.2.1 10.0.2.2 192.168.1.129 router eigrp 100 router eigrp 100 No auto-summary network 172.16.64.0 network 192.168.1.0 network 10.0.1.0 network 10.0.2.0 No auto-summary router eigrp 100 No auto-summary network 10.0.1.0 Network 10.0.2.0 IT2050| Computer Networks| Routing Protocols| Hansika Mahaadikara IT2050 - Computer Networks Lecture 5 Internet Protocol Ms. Hansika Mahaadikara IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Overview of IP IP is the network layer protocol of TCP/IP No Error control, flow control and congestion control Hence IP is an unreliable protocol Combination TCP/IP is reliable But UDP/IP is an unreliable combination IP packets operate as datagram IP packets originated from same source can travel through different routes and reach the destination at different times Therefore IP packets may reach the destination out of order IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Identification Each IP packet is identified by a serial number called “Identification” This sequence will be helpful to the receiver to reassemble the packets in the correct order, although they may receive in out of order IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Maximum Transmission Unit (MTU) Maximum amount of data that can be accommodated in a frame IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Fragmentation If the IP packet size is bigger than MTU, it should be fragmented Ex : If the original packet has 6000 bytes of data 1. Separate data and Header of IP Packet 2. Break data part into MTUs (Fragments) 3. Add 20 byte header to each fragment IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Fragmentation offset The identification of each fragmented IP packet is equal to identification of original IP packet Ex : If the identification of original IP packet is 2000, identification of all five fragments is 2000 “ Fragmentation offset ” is an another parameter used to identity the order of fragments IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Fragmentation offset cont. If the original packet has 6000 bytes of data , the numbering of data bytes are as follows Fragment 1 0 1479 Fragment 2 1480 2959 Fragment 3 2960 4439 Fragment 4 4440 5919 Fragment 5 5920 5999 IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Fragmentation offset cont. Offset value of fragment 1 = 0 = 0 8 Offset value of fragment 2 = 1480 = 185 8 Offset value of fragments 3 = 2960 = 370 8 Offset value of fragment 4 = 4440 = 555 8 Offset value of fragment 5 = 5920 = 740 8 IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Fragmentation offset cont. Fragmented packets travel independently They may travel through different routes to the destination While it is traveling it can be further fragmented at another intermediate network Original Packet Fragmented packets Fragmented packets IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Fragmentation offset cont. Fragmented packets reach to the destination out of order. The fragmented packets are combined (defragmented) at the final destination by using the OFFSET values. IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Time To Live (TTL) IP packets travel through many routers in the network Each router routes the packet according to information in the routing table If there is a problem in a routing table the packet may be sent in a wrong direction and it can be randomly flow in the network. This kind of IP packets can even overload the network and finally crash the network In order to avoid such a situation, a parameter called “Time To Live” (TTL) is defined for each IP packet IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Time To Live (TTL) cont. TTL value can be initialized to any value at the transmitting router (A) (maximum is 255) The TTL value is decremented at each router by 1 If the TTL value becomes zero at a router (B) , the packet will be discarded and an ICMP message is sent to the transmitted router(A) from the discarding router (B) IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Time To Live (TTL) cont. Suppose host A sends an IP packet to Host B The TTL value is set to 6 If the packet goes through Host A → R1 →R2 → R3 → Host B, Router TTL Value R1 = 5 R2 = 4 R3 = 3 IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Time To Live (TTL) cont. Suppose there is a routing problem and the packet loops through the routes R1 → R4 → R2 → R1→ R4 → R2 → R1 → R4 → R2 R1 R2 Router TTL Value Action R1 6 -1 = 5 R4 5–1=4 R4 R2 4–1=3 R1 3–1=2 R4 2–1=1 R2 1–1=0 Discards the Packet Send ICMP message to Host A The TTL value becomes zero at router R2 Therefore IP packet is discarded IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara IP header 32 bits 32 bits 32 bits IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Version (VER) A field of 4 bits Indicates the version of the using IP addresses in the IP packet IPv4 : 0100 IPv6 : 0110 IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Header Length (HLEN) A 4 bit field indicates the number of 4 bytes in the header Header size in bytes = HLEN x 4 The standard header size = 20 bytes 20 = 5 x 4 HLEN = 5 ( 0101 )2 The standard header size = 60 bytes 60 = 15 x 4 HLEN = 15 ( 1111 )2 IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Service Type A 8 bit field IETF has changed the name of this field as Differentiated Services 3 bits 4 bits Precedence TOS Not used  Precedence defines the priority of the packet  Precedence is not used in IPv4 IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Service Type cont. A 4-bit field Each bit has a special meaning There are five types of services IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Service Type cont. The application can select a specific type of service IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Total length A 16-bit field Gives the total length of the IP packet. Total length = data length + header length If total length value is 300 and if this is a normal IP packet Header length = 20 bytes Data length = 300 – 20 = 280 bytes IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Identification Each IP packet is identified by a serial number called “Identification” A 16 bit field The identification of each fragmented IP packet is equal to identification of original IP packet IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Flags D = 1, means is not allowed to be fragmented D = 0, means is allowed to be fragmented M = 0, means that there are no more fragments; The fragment is the last one. Non fragmented packet is considered the last fragment M = 1, The fragment is not the last one. IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Fragmentation offset A 13-bit field This gives the offset value of the fragment IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Time To Live (TTL) A 8 bit field Defines the maximum number of hops the packet can travel IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Protocol The IP packet data can be UDP, TCP, ICMP, IGMP, EGP Used to identify the type of data a special field called “protocol” 8-bit field which defines the protocol number IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Header Checksum A 16-bit field Checks the errors of the header only. If errors are found in the header, the whole IP packet is discarded. IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara Source IP Address A 32-bit field This gives the IP address of the source Destination IP Address A 32-bit field This gives the IP address of the destination IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara IP option IT2050| Computer Networks| Internet Protocol| Hansika Mahaadikara IT2050 – Computer Networks Lecture 06 Switched Networks IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Switch An intelligent device Operates in layer 2 – layer2 switch Operates in layer 3 – layer3 switch IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Form Factors Fixed Configuration Modular Configuration Stackable Configuration IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Business Considerations 0n Selecting switches Cost Speed and #of Interfaces , Supported Features Expansion Capability Port Density #of devices on the Network Power Power access points , PoE , Redundant Power Supply Reliability 24/7 Continues access Port Speed Ethernet , FastEthernet , GigabitEthernet Scalability Network growth IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Switch Functions Address learning Forward/filter decisions Loop avoidance IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Mac Address Table The switch learns the relationship of ports to devices, it builds a table called a MAC address. LAN switches determine how to handle incoming frames by maintaining the MAC address table. Switch builds its MAC address table by recording the MAC address of each device connected to each of its ports. The switch uses the information in the MAC address table to send frames destined for a specific device out the port which has been assigned to that device. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Address learning Layer 2 switches and bridges remember the source MAC address of each frame received on an interface, and they enter this information into a MAC database called a MAC address table IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Address learning cont. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Forward/filter decisions When a frame is received on an interface, the switch looks at the destination MAC address and finds the exit interface in the MAC address table Frame is only forwarded out the specified destination port IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Forward/filter decisions cont. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Loop Avoidance If multiple connections between switches are created for redundancy purposes, network loops can occur Spanning Tree Protocol (STP) is used to stop network loops while still permitting redundancy IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Switch Internal Processing IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Switch Internal Processing cont. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Frame Forwarding Store-and-Forward Switching Error Checking– After receiving the entire frame, the switch compares the frame-check-sequence (FCS) value in the last field against its own FCS calculations. Only error-free frames are forwarded Store-and-Forward is Cisco’s primary LAN switching method. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Frame Forwarding Cut-Through Switching Cut – Through Switching ( Rapid Frame Forwarding ) – The switch makes a forwarding decision as soon as it has looked up the destination MAC address. Frames with errors are forwarded. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Frame Forwarding Fragment Free Switching Fragment Free - modified form of cut-through switching. The switch waits for the collision window (64 bytes) to pass before forwarding the frame. Provides better error checking than cut-through, with practically no increase in latency. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Basic Switch Configurations Each port/interface does not need an IP address because the switch is not performing Layer 3 routing Can assign IP address to manage the switch or else IP would not be needed on the switch at all IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Configuring Basic Switch Management Access with IPv4 exit Important Concept The default gateway is the router address and is used by the switch to communicate with other networks. IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara Configure Switch Ports Verifying Switch Port Configuration IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara IT2050| Computer Networks| Basics of Switching| Hansika Mahaadikara IT2050 - Computer Networks Lecture 7 Securing Switched Networks IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara MAC Address Table Dynamic MAC addresses Sticky MAC addresses Permanent MAC addresses IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Port security limits the number of valid MAC addresses allowed to transmit data through a switch port. If a port has port security enabled and an unknown MAC address sends data, the switch presents a security violation. Default number of secure MAC addresses allowed is 1. IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Methods use to configure MAC addresses within port security: Static secure MAC addresses – manually configure switchport port-security mac-address mac-address Dynamic secure MAC addresses – dynamically learned and removed if the switch restarts Sticky secure MAC addresses – dynamically learned and added to the running configuration (which can later be saved to the startup-config to permanently retain the MAC addresses) switchport port-security mac-address sticky mac-address IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Dynamic MAC Addresses MAC addresses are added to the MAC address table through normal switch processing When a frame is received, the source MAC of the frame is associated with the incoming port/interface IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Permanent MAC addresses A MAC address is associated with a port Switch(config-if)#switchport mode access Switch(config-if)#switchport port-security Switch(config-if)#switchport port-security mac-address 0200.1111.1111 IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Switch Port Security Secure Unused Ports The interface range command can be used to apply a configuration to several switch ports at one time. IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Port Security Limits the number of MAC addresses associated with a port (limits number of sources that can forward frames into that switch port) Switch(config)#interface Switch(config-if)#switchport port-security maximum IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Port Security cont. Restrict port 0/1 so that only three MAC addresses can be learned on port 0/1 Switch(config)#interface Ethernet 0/1 Switch(config-if)# switchport port-security maximum 3 IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Address violation What should the switch do when a fourth MAC address sources a frame that enters E0/1? An address violation occurs when a secured port receives a frame from a new source address that, if added to the MAC table, would cause the switch to exceed its address table size limit for that port IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Switch Port Security Port Security: Violation Modes Protect – data from unknown source MAC addresses are dropped; a security notification IS NOT presented by the switch Restrict – data from unknown source MAC addresses are dropped; a security notification IS presented by the switch and the violation counter increments. Shutdown – (default mode) interface becomes error-disabled and port LED turns off. The violation counter increments. Issues the shutdown and then the no shutdown command on the interface to bring it out of the error-disabled state. IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Switch Port Security Port Security: Configuring IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Switch Port Security Port Security: Configuring (Cont.) Before configuring port-security features, place the port in access mode and use the switchport port-security interface configuration command to enable port security on an interface. IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Switch Port Security Port Security: Configuring (Cont.) IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara Switch Port Security Port Security: Verifying Use the show port-security interface command to verify the maximum number of MAC addresses allowed on a particular port and how many of those addresses were learned dynamically using sticky. Dynamic Sticky IT2050| Computer Networks | Securing Switched Networks | Hansika Mahaadikara IT2050 – Computer Networks Lecture 7 Virtual Local Area Networks (VLAN) Ms.Hansika Mahaadikara IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Sections & Objectives VLAN Segmentation Explain the purpose of VLANs in a switched network. Explain how a switch forwards frames based on VLAN configuration in a multi-switch environment. VLAN Implementations Configure a switch port to be assigned to a VLAN based on requirements. Configure a trunk port on a LAN switch. Troubleshoot VLAN and trunk configurations in a switched network. Inter-VLAN Routing Using Routers Describe the two options for configuring Inter-VLAN routing. Configure Router-on-a-Stick Inter-VLAN Routing IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Segmentation IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Broadcast Domains Three separate broadcast domains Requires three switches IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN cont. Each logical VLAN is like a separate physical switch – Each VLAN is a separate broadcast domain (3 broadcast domains) – Each VLAN contains a separate MAC address table – Computer in Blue VLAN will not be able to send a frame to Black VLAN or Green VLAN IT2050 | Computer Networks| VLAN | Hansika Mahaadikara IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Definitions (cont.) VLANs allow an administrator to segment networks based on factors such as function, project team, or application, without regard for the physical location of the user or device. VLANs enable the implementation of access and security policies according to specific groupings of users. A VLAN is a logical partition of a Layer 2 network. Multiple partitions can be created, allowing for multiple VLANs to co-exist. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Definitions (cont.) Each VLAN is a broadcast domain, usually with its own IP network. VLANs are mutually isolated, and packets can only pass between them via a router. The partitioning of the Layer 2 network takes place inside a Layer 2 device, usually via a switch. The hosts grouped within a VLAN are unaware of the VLAN’s existence. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Benefits of VLANs IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Types of VLANs Data VLAN – user generated traffic Default VLAN – all switch ports become part of this VLAN until switch is configured, Management VLAN – used to access management capabilities IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLANs in a Multi-Switched Environment VLAN Trunks The links between switches S1 and S2, and S1 and S3 are configured to transmit traffic coming from VLANs 10, 20, 30 the network. This network could not function without VLAN trunks. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLANs in a Multi-Switched Environment VLAN Trunks (cont.) A VLAN trunk is a point-to-point link that carries more than one VLAN. A VLAN trunk is usually established between switches so same-VLAN devices can communicate, even if physically connected to different switches. A VLAN trunk is not associated to any VLANs; neither is the trunk ports used to establish the trunk link. Cisco IOS supports IEEE802.1q, a popular VLAN trunk protocol. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN cont. VLANs can span across multiple switches IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN cont. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN tagging for source identification The process of adding an additional header to a LAN frame Used to identify the VLAN to which the frame belongs Cisco refers to this as TRUNKING Trunks carry traffic for multiple VLANs IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLANs in a Multi-Switched Environment Controlling Broadcast Domains with VLANs IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLANs in a Multi-Switched Environment Controlling Broadcast Domains with VLANs ❖VLANs can be used to limit the reach of broadcast frames. ❖A VLAN is a broadcast domain of its own. ❖A broadcast frame sent by a device in a specific VLAN is forwarded within that VLAN only. ❖VLANs help control the reach of broadcast frames and their impact in the network. ❖Unicast and multicast frames are forwarded within the originating VLAN. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Tagging Ethernet Frames for VLAN Identification Frame tagging is the process of adding a VLAN identification header to the frame. It is used to properly transmit multiple VLAN frames through a trunk link. Switches tag frames to identify the VLAN to which they belong. Different tagging protocols exist; ISL , IEEE 802.1Q. The protocol defines the structure of the tagging header added to the frame. Switches add VLAN tags to the frames before placing them into trunk links and remove the tags before forwarding frames through non-trunk ports. When properly tagged, the frames can transverse any number of switches via trunk links and still be forwarded within the correct VLAN at the destination. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Trunking There are two types of VLAN Trunking: - ISL (Inter-Switch Link) – Cisco Proprietary - IEEE 802.1Q IT2050 | Computer Networks| VLAN | Hansika Mahaadikara ISL (Inter-Switch Link) Full Ethernet frame is encapsulated with a ISL Indicate the VLAN ID (12 bit) to identify the VLAN CISCO proprietary IT2050 | Computer Networks| VLAN | Hansika Mahaadikara IEEE 802.1Q The IEEE 802.1Q tag is inserted by the switch before sending the frame across the trunk Indicate the VLAN ID (12 bit) to identify the VLAN IT2050 | Computer Networks| VLAN | Hansika Mahaadikara 802.1Q Tagging IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Trunks Configuring IEEE 802.1q Trunk Links IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Trunks Resetting the Trunk to Default State IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Troubleshoot VLANs and Trunks ▪ VLANs must be allowed in the trunk before their frames can be transmitted across the link. ▪ Use the switchport trunk allowed vlan command to specify which VLANs are allowed in a trunk link. ▪ Use the show interfaces trunk command to ensure the correct VLANs are permitted in a trunk. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Inter-VLAN Routing Using Routers IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Passing traffic between VLANs  Each VLAN will have different IP subnets  VLANs don’t send data frames to other VLAN (Separate MAC address table for each VLAN) IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Inter-VLAN Routing Layer 2 switches cannot forward traffic between VLANs without the assistance of a router. Inter-VLAN routing is a process for forwarding network traffic from one VLAN to another, using a router. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Inter-VLAN Routing Operation Legacy Inter-VLAN Routing In the past: Actual routers were used to route between VLANs. Each VLAN was connected to a different physical router interface. Packets would arrive on the router through one interface, be routed and leave through another. Because the router interfaces were connected to VLANs and had IP addresses from that specific VLAN, routing between VLANs was achieved. Large networks with large number of VLANs required many router interfaces. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Legacy Inter-VLAN Routing G0/2 172.17.20.1/24 In this example, the router was configured with three separate physical interfaces to interact with the different VLANs and perform the routing. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Passing traffic between VLANs cont. 10.1.0.0/16 10.2.0.0/16 - Three IP subnets 10.3.0.0/16 - Router with 3 LAN ports - Waste of resources IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Inter-VLAN Routing Operation Router-on-a-Stick Inter-VLAN Routing The router-on-a-stick approach uses only one of the router’s physical interface. One of the router’s physical interfaces is configured as a 802.1Q trunk port so it can understand VLAN tags. Logical sub-interfaces are created; one sub- interface per VLAN. Each sub-interface is configured with an IP address from the VLAN it represents. VLAN members (hosts) are configured to use the sub- interface address as a default gateway. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Passing traffic between VLANs cont.  Solution Router supports trunking (Inter VLAN routing) - Single physical connection - Single Fast Ethernet port 10.1.0.0/16 10.2.0.0/16 10.3.0.0/16 IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Inter VLAN routing Sub interfaces on a router can be used to divide a single physical interface into multiple logical interfaces Each physical interface can have up to 65,535 logical interfaces IT2050 | Computer Networks| VLAN | Hansika Mahaadikara IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Configure Router-on-a Stick: VLAN trunking allows a single physical router interface to route traffic for multiple VLANs. The physical interface of the router must be connected to a trunk link on the adjacent switch. On the router, sub-interfaces are created for each unique VLAN. Each sub-interface is assigned an IP address specific to its subnet or VLAN and is also configured to tag frames for that VLAN. IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Configure Router-on-a Stick: Switch Configuration IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Configure Router-on-a Stick: Router Subinterface Configuration IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Configure Router-on-a Stick: Verifying Subinterfaces (cont.) IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Implementations IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Types of VLANs (cont.) IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Ranges on Catalyst Switches Cisco Catalyst 2960 and 3560 Series switches support over 4,000 VLANs. VLANs are split into two categories: Normal range VLANs VLAN numbers from 1 to 1,005 Configurations stored in the vlan.dat (in the flash memory) IDs 1002 through 1005 are reserved for Token Ring and Fiber Distributed Data Interface (FDDI) VLANs, automatically created and cannot be removed Extended Range VLANs VLAN numbers from 1,006 to 4,096 Configurations stored in the running configuration (NVRAM) VLAN Trunking Protocol (VTP) does not learn extended VLANs IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Ranges on Catalyst Switches Normal Range VLANs IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Assignment Creating a VLAN IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Assignment Assigning Ports to VLANs IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Changing VLAN Port Membership Remove VLAN Assignment ▪ Interface F0/18 was previously assigned to VLAN 20 which is still active, F0/18 reset to VLAN1 IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Assignment Changing VLAN Port Membership (cont.) IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Deleting VLANs IT2050 | Computer Networks| VLAN | Hansika Mahaadikara VLAN Assignment Verifying VLAN Information IT2050 | Computer Networks| VLAN | Hansika Mahaadikara Verifying VLAN Information IT2050 | Computer Networks| VLAN | Hansika Mahaadikara

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