CISCO 1-9 REVIEWER PDF

Static Routing Static Route Characteristics: Must be configured manually Must be adjusted manually by the administrator when there is a change in the topology Good for small non-redundant networks Often used in conjunction with a dynamic routing protocol for...

Static Routing Static Route Characteristics: Must be configured manually Must be adjusted manually by the administrator when there is a change in the topology Good for small non-redundant networks Often used in conjunction with a dynamic routing protocol for configuring a default route INTRODUCTION TO AN IPV4 ROUTING TABLE The show ip route command shows the following route sources: L - Directly connected local interface IP address C – Directly connected network S – Static route was manually configured by an administrator O – OSPF D – EIGRP This command shows types of routes: Directly Connected – C and L Remote Routes – O, D, etc. Default Routes – S* Dynamic Routing Dynamic Routes Automatically: Discover remote networks Maintain up-to-date information Choose the best path to the destination Find new best paths when there is a topology change Dynamic routing can also share static default routes with the other routers  Local traffic is dumped out the host interface to be Host Routing Tables handled by an intermediary device. On Windows, route print or netstat -r to display the Remote traffic is forwarded directly to the default PC routing table gateway on the LAN. Three sections displayed by these two commands: Default Gateway Interface List – all potential interfaces and MAC addressing A router or layer 3 switch can be a default-gateway. IPv4 Routing Table Features of a default gateway (DGW): IPv6 Routing Table It must have an IP address in the same range as the rest of the LAN. It can accept data from the LAN and is capable of forwarding traffic off of the LAN. It can route to other networks. If a device has no default gateway or a bad default gateway, its traffic will not be able to leave the LAN. A Host Routes to the Default Gateway The host will know the default gateway (DGW) either statically or through DHCP in IPv4. IPv6 sends the DGW through a router solicitation (RS) or can be configured manually. INTRODUCTION TO ROUTING A DGW is static route which will be a last resort Router Packet Forwarding Decision route in the routing table. All device on the LAN will need the DGW of the router if they intend to send traffic remotely. THREE TYPES OF ROUTES IN A ROUTER’S ROUTING TABLE: Directly Connected – These routes are automatically added by the router, provided the interface is active and has addressing. Remote – These are the routes the router does not have a direct connection and may be learned: Manually – with a static route Dynamically – by using a routing protocol to have the routers share their information with each other Default Route – this forwards all traffic to a specific direction when there is not a match in the routing table  Improvements that IPv6 provides: Increased address space – based on 128 bit address, not 32 bits Improved packet handling – simplified header with fewer fields Eliminates the need for NAT – since there is a huge amount of addressing, there is no need to use private addressing internally and be mapped to a shared public address IPv6 packet may also contain extension headers (EH). EH headers characteristics: provide optional network layer information are optional are placed between IPv6 header and the payload may be used for fragmentation, security, mobility support, etc. Unlike IPv4, routers do not fragment IPv6 packets. Host Forwarding Decision Packets are always created at the source. Each host devices creates their own routing table. IPv4 Packet Header Fields in the IPv6 Packet Header A host can send packets to the following: The IPv6 header is simplified, but not smaller. Itself – 127.0.0.1 (IPv4), ::1 (IPv6) The header is fixed at 40 Bytes or octets long. Local Hosts – destination is on the same LAN Several IPv4 fields were removed to improve performance. Remote Hosts – devices are not on the same LAN Some IPv4 fields were removed to improve performance: Flag Fragment Offset Header Checksum The Source device determines whether the destination is local or remote Method of determination: IPv4 – Source uses its own IP address and Subnet mask, along with the destination IP address IPv6 – Source uses the network address and prefix advertised by the local router The network layer will establish the Maximum Transmission Unit (MTU). Network layer receives this from control information sent by the data link layer. The network then establishes the MTU size. Fragmentation is when Layer 3 splits the IPv4 packet into smaller units. Fragmenting causes latency. IPv6 does not fragment packets. Example: Router goes from Ethernet to a slow WAN with a smaller MTU IPv4 PACKET IPv4 Packet Header IPv4 is the primary communication protocol for the network layer. The network header has many purposes: It ensures the packet is sent in the correct direction (to the destination). It contains information for network layer processing in various fields. The information in the header is used by all layer 3 devices that handle the packet IPv6 PACKETS IPv4 Packet Header Fields Limitations of IPv4 The IPv4 network header characteristics: IPv4 has three major limitations: It is in binary. IPv4 address depletion – We have basically run Contains several fields of information out of IPv4 addressing. Lack of end-to-end connectivity – To make IPv4 Diagram is read from left to right, 4 bytes per line survive this long, private addressing and NAT were The two most important fields are the source and created. This ended direct communications with destination. public addressing. Protocols may have may have one or more Increased network complexity – NAT was meant functions. as temporary solution and creates issues on the network as a side effect of manipulating the network headers addressing. NAT causes latency and troubleshooting issues. IPv6 was developed by Internet Engineering Task Force (IETF). IPv6 overcomes the limitations of IPv4.  MAC addressing provides a method for device Characteristics of IP identification at the data link layer of the OSI model. Connectionless An Ethernet MAC address is a 48-bit address IP does not establish a connection with the expressed using 12 hexadecimal digits, or 6 destination before sending the packet. bytes. There is no control information needed When a device is forwarding a message to an (synchronizations, acknowledgments, etc.). Ethernet network, the Ethernet header includes the The destination will receive the packet when it source and destination MAC addresses. In arrives, but no pre-notifications are sent by IP. Ethernet, different MAC addresses are used for Layer 2 unicast, broadcast, and multicast If there is a need for connection-oriented traffic, communications. then another protocol will handle this (typically TCP at the transport layer). A Layer 2 Ethernet switch makes its forwarding decisions based solely on the Layer 2 Ethernet MAC addresses. The switch dynamically builds the MAC address Best Effort table by examining the source MAC address of the IP will not guarantee delivery of the packet. frames received on a port. The switch forwards frames by searching for a IP has reduced overhead since there is no match between the destination MAC address in the mechanism to resend data that is not received. frame and an entry in the MAC address table. Switches use one of the following forwarding IP does not expect acknowledgments. methods for switching data between network ports: IP does not know if the other device is operational store-and-forward switching or cut-through switching. Two variants of cut-through switching or if it received the packet. are fast-forward and fragment-free. Media Independent NETWORK LAYER IP is unreliable: Network Layer Characteristics It cannot manage or fix undelivered or corrupt Provides services to allow end devices to exchange data packets. IP version 4 (IPv4) and IP version 6 (IPv6) are the IP cannot retransmit after an error. principle network layer communication protocols. The network layer performs four basic operations: IP cannot realign out of sequence packets. Addressing end devices Encapsulation IP must rely on other protocols for these functions. Routing IP is media Independent: De-encapsulation IP does not concern itself with the type of frame IP Encapsulation required at the data link layer or the media type at IP encapsulates the transport layer segment. the physical layer. IP can use either an IPv4 or IPv6 packet and not impact the layer 4 segment. IP can be sent over any media type: copper, fiber, IP packet will be examined by all layer 3 devices or wireless. as it traverses the network. The IP addressing does not change from source to destination. SWITCH SPEEDS AND FORWARDING METHODS MEMORY BUFFERING ON SWITCHES Port-based memory - Frames are stored in queues that Frame Forwarding Methods on Cisco Switches are linked to specific incoming and outgoing ports. A frame is transmitted to the outgoing port only when all the Store-and-forward switching - This frame frames ahead in the queue have been successfully forwarding method receives the entire frame and transmitted. It is possible for a single frame to delay the computes the CRC. If the CRC is valid, the switch transmission of all the frames in memory because of a looks up the destination address, which busy destination port. This delay occurs even if the other determines the outgoing interface. Then the frame frames could be transmitted to open destination ports is forwarded out of the correct port. Shared memory - Deposits all frames into a common Cut-through switching - This frame forwarding memory buffer shared by all switch ports and the amount method forwards the frame before it is entirely of buffer memory required by a port is dynamically received. At a minimum, the destination address of allocated. The frames in the buffer are dynamically linked the frame must be read before the frame can be to the destination port enabling a packet to be received on forwarded. one port and then transmitted on another port, without A big advantage of store-and-forward switching is that moving it to a different queue. it determines if a frame has errors before propagating the Shared memory buffering also results in larger frames frame. When an error is detected in a frame, the switch that can be transmitted with fewer dropped frames. This is discards the frame. Discarding frames with errors reduces important with asymmetric switching which allows for the amount of bandwidth consumed by corrupt data. different data rates on different ports. Therefore, more Store-and-forward switching is required for quality of bandwidth can be dedicated to certain ports (e.g., server port). service (QoS) analysis on converged networks where frame classification for traffic prioritization is necessary. For example, voice over IP (VoIP) data streams need to DUPLEX AND SPEED SETTINGS have priority over web-browsing traffic. 2 Types of Duplex settings Full-duplex - Both ends of the connection can In cut-through switching, the switch acts upon the data as send and receive simultaneously. soon as it is received, even if the transmission is not complete. The switch buffers just enough of the frame to Half-duplex - Only one end of the connection can read the destination MAC address so that it can determine send at a time to which port it should forward out the data. The switch Duplex mismatch is one of the most common causes of does not perform any error checking on the frame. performance issues on 10/100 Mbps Ethernet links. It There are two variants of cut-through switching: occurs when one port on the link operates at half-duplex while the other port operates at full-duplex. Fast-forward switching - Offers the lowest level of latency by immediately forwarding a packet after AUTO MDIX - Connections between devices once reading the destination address. Because fast- required the use of either a crossover or straight-through forward switching starts forwarding before the cable. The type of cable required depended on the type of entire packet has been received, there may be interconnecting devices. times when packets are relayed with errors. The Auto-MDIX can be re-enabled using the mdix destination NIC discards the faulty packet upon auto interface configuration command. receipt. Fast-forward switching is the typical cut- through method of switching. Ethernet operates in the data link layer and the physical layer. Ethernet standards define both the Fragment-free switching - A compromise between the Layer 2 protocols and the Layer 1 technologies. high latency and high integrity of store-and-forward switching and the low latency and reduced integrity of fast- Ethernet uses the LLC and MAC sublayers of the forward switching, the switch stores and performs an error data link layer to operate. check on the first 64 bytes of the frame before forwarding. The Ethernet frame fields are: preamble and start Because most network errors and collisions occur during frame delimiter, destination MAC address, the first 64 bytes, this ensures that a collision has not source MAC address, EtherType, data, and FCS. occurred before forwarding the frame.  Because multicast addresses represent a group of SWITCH LEARNING AND FORWARDING addresses (sometimes called a host group), they can only be used as the destination of a packet. Examine the Source MAC Address (Learn) The source will always be a unicast address. Every frame that enters a switch is checked for As with the unicast and broadcast addresses, the new information to learn. It does this by examining multicast IP address requires a corresponding the source MAC address of the frame and the port multicast MAC address. number where the frame entered the switch. If the source MAC address does not exist, it is added to the table along with the incoming port number. If the source MAC address does exist, the switch updates the refresh timer for that entry. By default, most Ethernet switches keep an entry in the table for 5 minutes. If the source MAC address does exist in the table but on a different port, the switch treats this as a new entry. The entry is replaced using the same MAC address but with the more current port number. Find the Destination MAC Address (Forward) If the destination MAC address is a unicast address, the switch will look for a match between the destination MAC address of the frame and an THE MAC ADDRESS TABLE entry in its MAC address table. If the destination MAC address is in the table, it will forward the Switch Fundamentals frame out the specified port. If the destination MAC A Layer 2 Ethernet switch uses Layer 2 MAC address is not in the table, the switch will forward addresses to make forwarding decisions. It is the frame out all ports except the incoming port. completely unaware of the data (protocol) being This is called an unknown unicast. carried in the data portion of the frame, such as an If the destination MAC address is a broadcast or a IPv4 packet, an ARP message, or an IPv6 ND multicast, the frame is also flooded out all ports packet. The switch makes its forwarding decisions except the incoming port. based solely on the Layer 2 Ethernet MAC addresses. An Ethernet switch examines its MAC address FILTERING FRAME table to make a forwarding decision for each frame, unlike legacy Ethernet hubs that repeat bits As a switch receives frames from different devices, out all ports except the incoming port. it is able to populate its MAC address table by examining the source MAC address of every When a switch is turned on, the MAC address frame. When the MAC address table of the switch table is empty contains the destination MAC address, it is able to The MAC address table is sometimes referred to filter the frame and forward out a single port. as a content addressable memory (CAM) table  To ensure this, all vendors that sell Ethernet BROADCAST MAC ADDRESS devices must register with the IEEE to obtain a unique 6 hexadecimal (i.e., 24-bit or 3-byte) code An Ethernet broadcast frame is received and processed called the organizationally unique identifier (OUI). by every device on the Ethernet LAN. The features of an Ethernet broadcast are as follows: An Ethernet MAC address consists of a 6 hexadecimal vendor OUI code followed by a 6 It has a destination MAC address of FF-FF-FF-FF- hexadecimal vendor-assigned value. FF-FF in hexadecimal (48 ones in binary). It is flooded out all Ethernet switch ports except the incoming port. It is not forwarded by a router. FRAME PROCESSING If the encapsulated data is an IPv4 broadcast When a device is forwarding a message to an packet, this means the packet contains a Ethernet network, the Ethernet header include a destination IPv4 address that has all ones (1s) in Source MAC address and a Destination MAC the host portion. This numbering in the address address. means that all hosts on that local network (broadcast domain) will receive and process the When a NIC receives an Ethernet frame, it packet. examines the destination MAC address to see if it matches the physical MAC address that is stored in RAM. If there is no match, the device discards the frame. If there is a match, it passes the frame up the OSI layers, where the de-encapsulation process takes place. Ethernet NICs will also accept frames if the destination MAC address is a broadcast or a multicast group of which the host is a member. Any device that is the source or destination of an Ethernet frame, will have an Ethernet NIC and therefore, a MAC address. This includes workstations, servers, printers, mobile devices, and routers. UNICAST MAC ADDRESS - is the unique address that is used when a frame is sent from a single MULTICAST MAC ADDRESS transmitting device to a single destination device. An Ethernet multicast frame is received and processed by a group of devices that belong to the same multicast group. There is a destination MAC address of 01-00-5E when the encapsulated data is an IPv4 multicast packet and a destination MAC address of 33-33 when the encapsulated data is an IPv6 multicast packet. There are other reserved multicast destination MAC addresses for when the encapsulated data is not IP, such as Spanning Tree Protocol (STP). It is flooded out all Ethernet switch ports except the incoming port, unless the switch is configured for multicast snooping. It is not forwarded by a router, unless the router is configured to route multicast packets. LAYER 2 ADDRESSES Data Encapsulation Also referred to as a physical address. IEEE 802.3 data encapsulation includes the following: Contained in the frame header. 1. Ethernet frame - This is the internal structure of the Ethernet frame. Used only for local delivery of a frame on the link. 2. Ethernet Addressing - The Ethernet frame Updated by each device that forwards the frame. includes both a source and destination MAC address to deliver the Ethernet frame from Ethernet NIC to Ethernet NIC on the same LAN. LAN AND WAN FRAMES 3. Ethernet Error detection - The Ethernet frame The logical topology and physical media determine the includes a frame check sequence (FCS) trailer data link protocol used: used for error detection. Ethernet Ethernet Frame Fields 802.11 Wireless The minimum Ethernet frame size is 64 bytes Point-to-Point (PPP) and the maximum is 1518 bytes. The preamble field is not included when describing the size of the High-Level Data Link Control (HDLC) frame. Frame-Relay Any frame less than 64 bytes in length is Each protocol performs media access control for specified considered a “collision fragment” or “runt logical topologies. frame” and is automatically discarded. Frames with more than 1500 bytes of data are considered The data link layer of the OSI model (Layer 2) “jumbo” or “baby giant frames”. prepares network data for the physical network. If the size of a transmitted frame is less than the The data link layer is responsible for network minimum, or greater than the maximum, the interface card (NIC) to network interface card receiving device drops the frame. Dropped frames communications. are likely to be the result of collisions or other unwanted signals. They are considered invalid. Data link addresses are also known as physical Jumbo frames are usually supported by most Fast addresses. Ethernet and Gigabit Ethernet switches and NICs. Data link addresses are only used for link local delivery of frames. ETHERNET FRAMES Ethernet Encapsulation - operates in the data link layer and the physical layer. It is a family of networking technologies defined in the IEEE 802.2 and 802.3 standards. DATALINK SUBLAYERS The 802 LAN/MAN standards, including Ethernet, use two Ethernet MAC Address separate sublayers of the data link layer to operate: consists of a 48-bit binary value, expressed using LLC Sublayer: (IEEE 802.2) Places information in 12 hexadecimal values. the frame to identify which network layer protocol is a 48-bit address expressed using 12 is used for the frame. hexadecimal digits. byte equals 8 bits, we can also say that a MAC MAC Sublayer: (IEEE 802.3, 802.11, or 802.15) address is 6 bytes in length. Responsible for data encapsulation and media All MAC addresses must be unique to the Ethernet access control, and provides data link layer device or Ethernet interface. addressing. MAC Sublayer - is responsible for data encapsulation and accessing the media.  HALF AND FULL DUPLEX COMMUNICATION CSMA/CA Half-duplex communication Used by IEEE 802.11 WLANs. Only allows one device to send or receive at a time Operates in half-duplex mode where only one on a shared medium. device sends or receives at a time. Used on WLANs and legacy bus topologies with Uses a collision avoidance process to govern Ethernet hubs. when a device can send and what happens if multiple devices send at the same time. Full-duplex communication Allows both devices to simultaneously transmit and receive on a shared medium. CSMA/CA collision avoidance process: Ethernet switches operate in full-duplex mode When transmitting, devices also include the time duration needed for the transmission. Other devices on the shared medium receive the ACCESS CONTROL METHODS time duration information and know how long the Contention-based access medium will be unavailable. All nodes operating in half-duplex, competing for use of the medium. Examples are: DATA LINK FRAME Carrier sense multiple access with collision The Frame detection (CSMA/CD) as used on legacy bus- topology Ethernet. Data encapsulated by the data link layer with a header and a trailer to form a frame. Carrier sense multiple access with collision avoidance (CSMA/CA) as used on Wireless LANs. A data link frame has three basic parts: Controlled access Header Deterministic access where each node has its own Data time on the medium. Trailer Used on legacy networks such as Token Ring and ARCNET. The fields of the header and trailer vary according to data link layer protocol. The amount of control information carried with in the CONTENTION-BASED ACCESS – CSMA/CD frame varies according to access control information and logical topology. CSMA/CD FRAME FIELDS Used by legacy Ethernet LANs. Operates in half-duplex mode where only one device sends or receives at a time. Uses a collision detection process to govern when a device can send and what happens if multiple devices send at the same time. Frame Start and Stop - Identifies beginning and end of CSMA/CD collision detection process: frame Devices transmitting simultaneously will result in a Addressing - Indicates source and destination nodes signal collision on the shared media. Type - Identifies encapsulated Layer 3 protocol Devices detect the collision. Control - Identifies flow control services Devices wait a random period of time and retransmit data. Data - Contains the frame payload Error Detection - Used for determine transmission errors  IEEE 802 LAN/MAN Data Link Sublayers WAN TOPOLOGIES IEEE 802 LAN/MAN standards are specific to the type of Three common physical WAN topologies: network (Ethernet, WLAN, WPAN, etc). Point-to-point – the simplest and most common The Data Link Layer consists of two sublayers. WAN topology. Consists of a permanent link between two endpoints. Logical Link Control (LLC) Media Access Control (MAC). Hub and spoke – similar to a star topology where a central site interconnects branch sites through The LLC sublayer communicates between the point-to-point links. networking software at the upper layers and the device hardware at the lower layers. Mesh – provides high availability but requires every end system to be connected to every other The MAC sublayer is responsible for data end system. encapsulation and media access control. POINT TO POINT WAN TOPOLOGY Physical point-to-point topologies directly connect two nodes. The nodes may not share the media with other hosts. Because all frames on the media can only travel to or from the two nodes, Point-to-Point WAN protocols can be very simple. LAN TOPOLOGIES End devices on LANs are typically interconnected using a star or extended star topology. Star and extended star topologies are easy to install, very scalable and easy to troubleshoot. Early Ethernet and Legacy Token Ring technologies provide two additional topologies: Bus – All end systems chained together and terminated on each end. Data link layer protocols are defined by engineering organizations: Ring – Each end system is connected to its respective neighbors to form a ring. Institute for Electrical and Electronic Engineers (IEEE). International Telecommunications Union (ITU). International Organizations for Standardization (ISO). American National Standards Institute (ANSI) PHYSICAL AND LOGICAL TOPOLOGIES\ Topology of a network is the arrangement and relationship of the network devices and the interconnections between them. Physical topology – shows physical connections and how devices are interconnected. Logical topology – identifies the virtual connections between devices using device interfaces and IP addressing schemes. Hexadecimal and IPv6 Addresses DECIMAL TO HEXADECIMAL CONVERSIONS To understand IPv6 addresses, you must be able Convert the decimal number to 8-bit binary strings. to convert hexadecimal to decimal and vice versa. Divide the binary strings in groups of four starting Hexadecimal is a base sixteen numbering system, from the rightmost position. using the digits 0 through 9 and letters A to F. Convert each four binary numbers into their It is easier to express a value as a single equivalent hexadecimal digit. hexadecimal digit than as four binary bit. For example, 168 converted into hex using the three-step Hexadecimal is used to represent IPv6 addresses process. and MAC addresses. 168 in binary is 10101000. 10101000 in two groups of four binary digits is 1010 and 1000. 1010 is hex A and 1000 is hex 8, so 168 is A8 in hexadecimal. Convert the hexadecimal number to 4-bit binary strings. Create 8-bit binary grouping starting from the rightmost position. Convert each 8-bit binary grouping into their equivalent decimal digit. For example, D2 converted into decimal using the three- IPv6 addresses are 128 bits in length. Every 4 bits step process: is represented by a single hexadecimal digit. That D2 in 4-bit binary strings is 1110 and 0010. makes the IPv6 address a total of 32 hexadecimal values. 1110 and 0010 is 11100010 in an 8-bit grouping. The figure shows the preferred method of writing 11100010 in binary is equivalent to 210 in decimal, out an IPv6 address, with each X representing four so D2 is 210 is decimal hexadecimal values. Each four hexadecimal character group is referred Binary is a base two numbering system that consists of to as a hextet. the numbers 0 and 1, called bits. Hexadecimal is a base sixteen numbering system that consists of the numbers 0 through 9 and the letters A to F. DATA LINK LAYER - is responsible for communications between end-device network interface cards. It allows upper layer protocols to access the physical layer media and encapsulates Layer 3 packets (IPv4 and IPv6) into Layer 2 Frames. It also performs error detection and rejects corrupts frames. Binary Number System - Calculate numbers between DECIMAL TO BINARY VERSION decimal and it consists of 1s and 0s, called bits The binary positional value table is useful in converting a Decimal numbering system - consists of digits 0-9 dotted decimal IPv4 address to binary. Hexadecimal Number System - Calculate numbers start in the 128 position (the most significant bit). Is between decimal and hexadecimal systems. the decimal number of the octet (n) equal to or greater than 128? Hosts, servers, and network equipment using binary addressing to identify each other. If no, record a binary 0 in the 128 positional value and move to the 64 positional value. Each address is made up of a string of 32 bits, divided into four sections called octets. If yes, record a binary 1 in the 128 positional value, subtract 128 from the decimal number, and move Each octet contains 8 bits (or 1 byte) separated by to the 64 positional value. a dot. Repeat these steps through the 1 positional value. For ease of use by people, this dotted notation is converted to dotted decimal. BINARY POSITIONAL NOTATION Positional notation - means that a digit represents different values depending on the “position” the digit occupies in the sequence of numbers. CONVERT BINARY TO DECIMAL IPV4 ADDRESSES - Routers and computers only understand binary, while humans work in decimal. It is important for you to gain a thorough understanding of these two numbering systems and how they are used in networking.  FIBER OPTIC CABLING USAGE Fiber-optic cabling is now being used in four types of industry: 1. Enterprise Networks - Used for backbone cabling applications and interconnecting infrastructure devices 2. Fiber-to-the-Home (FTTH) - Used to provide always-on broadband services to homes and small businesses Wireless Media - it carries electromagnetic signals representing binary digits using radio or microwave 3. Long-Haul Networks - Used by service providers frequencies. This provides the greatest mobility option. to connect countries and cities Wireless connection numbers continue to increase. 4. Submarine Cable Networks - Used to provide Some of the limitations of wireless: reliable high-speed, high-capacity solutions capable of surviving in harsh undersea Coverage area - Effective coverage can be environments at up to transoceanic distances. significantly impacted by the physical characteristics of the deployment location. Interference - Wireless is susceptible to FIBER OPTIC CONNECTORS interference and can be disrupted by many common devices. Security - Wireless communication coverage requires no access to a physical strand of media, so anyone can gain access to the transmission. Shared medium - WLANs operate in half-duplex, which means only one device can send or receive at a time. Many users accessing the WLAN simultaneously results in reduced bandwidth for each user. TYPES OF WIRELESS MEDIA FIBER PATCH CORDS Wi-Fi (IEEE 802.11) - Wireless LAN (WLAN) technology Bluetooth (IEEE 802.15) - Wireless Personal Area network (WPAN) standard WiMAX (IEEE 802.16) - Uses a point-to-multipoint topology to provide broadband wireless access Zigbee (IEEE 802.15.4) - Low data-rate, low power-consumption communications, primarily for A yellow jacket is for single-mode fiber cables and Internet of Things (IoT) applications orange (or aqua) for multimode fiber cables. Optical fiber - is primarily used as backbone cabling for high-traffic, point-to-point connections between data In general, a Wireless LAN (WLAN) requires the following distribution facilities and for the interconnection of devices: buildings in multi-building campuses. Wireless Access Point (AP) - Concentrate wireless signals from users and connect to the existing copper-based network infrastructure Wireless NIC Adapters - Provide wireless communications capability to network hosts  FIBER-OPTIC CABLING Not as common as UTP because of the expense involved Ideal for some networking scenarios Transmits data over longer distances at higher bandwidth than any other networking media Less susceptible to attenuation, and completely immune to EMI/RFI Made of flexible, extremely thin strands of very pure glass Uses a laser or LED to encode bits as pulses of light The fiber-optic cable acts as a wave guide to transmit light between the two ends with minimal signal loss TYPE OF FIBER MEDIA Single-Mode Fiber Very small core Uses expensive lasers Long-distance applications Straight-through and Crossover UTP Cables Multimode Fiber Larger core Uses less expensive LEDs LEDs transmit at different angles Up to 10 Gbps over 550 meters Dispersion - refers to the spreading out of a light pulse over time. Increased dispersion means increased loss of signal strength. MMF has greater dispersion than SMF, with a the maximum cable distance for MMF is 550 meters.  TYPE OF COPPER CABLING Different Types of Connectors used in Coaxial Cable Wireless installations - attach antennas to wireless devices Cable internet installations - customer premises wiring Unshielded Twisted-Pair (UTP) Cable - is the most common networking media. Terminated with RJ-45 connectors and interconnects hosts with intermediary network devices. Key Characteristics of UTP UTP CABLING 1. The outer jacket protects the copper wires from UTP - has four pairs of color-coded copper wires twisted physical damage. together and encased in a flexible plastic sheath. No shielding is used. 2. Twisted pairs protect the signal from interference. UTP relies on the following properties to limit crosstalk: 3. Color-coded plastic insulation electrically isolates the wires from each other and identifies each pair. Cancellation - Each wire in a pair of wires uses opposite polarity. One wire is negative, the other Shieled Twisted Pair (STP) - Better noise protection than wire is positive. They are twisted together and the UTP. More expensive than UTP. Harder to install than magnetic fields effectively cancel each other and UTP. Terminated with RJ-45 connectors and interconnects outside EMI/RFI. hosts with intermediary network devices. Variation in twists per foot in each wire - Each Key Characteristics of STP wire is twisted a different amount, which helps prevent crosstalk amongst the wires in the cable. 1. The outer jacket protects the copper wires from physical damage 2. Braided or foil shield provides EMI/RFI protection UTP CABLING STANDARDS AND CONNECTORS 3. Foil shield for each pair of wires provides EMI/RFI Standards for UTP are established by the TIA/EIA. protection TIA/EIA-568 standardizes elements like: 4. Color-coded plastic insulation electrically isolates Cable Types the wires from each other and identifies each pair Cable Lengths Connectors Coaxial Cable Cable Termination Outer cable jacket to prevent minor physical damage Testing Methods A woven copper braid, or metallic foil, acts as the Electrical standards for copper cabling are established by second wire in the circuit and as a shield for the the IEEE, which rates cable according to its performance. inner conductor. Examples include: A layer of flexible plastic insulation A copper conductor is used to transmit the Category 3 electronic signals. Category 5 and 5e Category 6 DATA LINK ADDRESSES Signaling - how the bit values, “1” and “0” are represented on the physical medium. Since data link addressing is local addressing, it will have a source and destination for each Bandwidth - is the capacity at which a medium can carry segment or hop of the journey to the destination. data. The MAC addressing for the first segment is: Digital bandwidth - measures the amount of data that can flow from one place to another in a given amount of Source – (PC1 NIC) sends frame time; how many bits can be transmitted in a second. Destination – (First Router- DGW interface) receives frame The MAC addressing for the second hop is: Source – (First Router- exit interface) sends frame Destination – (Second Router) receives frame Bandwidth Terminology The MAC addressing for the last segment is: Latency - Amount of time, including delays, for data to Source – (Second Router- exit interface) sends travel from one given point to another frame Throughput - The measure of the transfer of bits across Destination – (Web Server NIC) receives frame the media over a given period of time Goodput – the measure of usable data transferred over a Physical Layer - Transports bits across the network given period of time media. This is the last step in the encapsulation process. Goodput = Throughput - traffic overhead PHYSICAL LAYER STANDARDS Copper Cabling - is the most common type of cabling used in networks today. It is inexpensive, easy to install, and has low resistance to electrical current flow. Limitations: Attenuation – the longer the electrical signals have to travel, the weaker they get. The electrical signal is susceptible to interference from two sources, which can distort and corrupt the data signals (Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) and Crosstalk). PHYSICAL LAYER STANDARDS ADDRESS THREE Mitigation: FUNCTIONAL AREAS: Strict adherence to cable length limits will mitigate Physical Components attenuation. Encoding Some kinds of copper cable mitigate EMI and RFI Signaling by using metallic shielding and grounding. Physical Components - are the hardware devices like Some kinds of copper cable mitigate crosstalk by NICs, interfaces and connectors, cable materials and twisting opposing circuit pair wires together. cable designs, media, and other connectors that transmit the signals that represent the bits. Encoding - converts the stream of bits into a format recognizable by the next device in the network path.  DATA ACCESS Role of the Data Link Layer Addresses: Same IP Network Addresses - Both the data link and network layers use addressing to deliver data from source to final destination. When devices are on the same Ethernet network the data link frame will use the actual MAC address of the Network layer source and destination addresses - destination NIC. Responsible for delivering the IP packet from original source to the final destination. MAC addresses are physically embedded into the Ethernet NIC and are local addressing. Data link layer source and destination addresses – Responsible for delivering the data link frame from one The Source MAC address will be that of the network interface card (NIC) to another NIC on the same originator on the link. network. The Destination MAC address will always be on the same link as the source, even if the ultimate destination is remote. Role of the Network Layer Addresses When the source and destination have a different network portion, this means they are on different networks. LAYER 3 LOGICAL ADDRESS PC1 – 192.168.1 The IP packet contains two IP addresses: Web Server – 172.16. Source IP address - The IP address of the sending device, original source of the packet. Role of the Data Link Layer Addresses: Different IP Destination IP address - The IP address of the Network receiving device, final destination of the packet. When the final destination is remote, Layer 3 will provide These addresses may be on the same link or remote. Layer 2 with the local default gateway IP address, also known as the router address. An IP address contains two parts: The default gateway (DGW) is the router interface IP address that is part of this LAN and will be the Network portion (IPv4) or Prefix (IPv6) “door” or “gateway” to all other remote locations. The left-most part of the address indicates All devices on the LAN must be told about this the network group which the IP address is a address or their traffic will be confined to the LAN member. only. Each LAN or WAN will have the same Once Layer 2 on PC1 forwards to the default network portion. gateway (Router), the router then can start the Host portion (IPv4) or Interface ID (IPv6) routing process of getting the information to actual destination. The remaining part of the address identifies a specific device within the group. The data link addressing is local addressing so it will have a source and destination for each link. This portion is unique for each device on the network. The MAC addressing for the first segment i: Device on the Same Network Source – AA-AA-AA-AA-AA-AA (PC1) Sends the frame. When devices are on the same network the source and destination will have the same number in network portion Destination – 11-11-11-11-11-11 (R1- of the address. Default Gateway MAC) Receives the frame. PC1 – 192.168.1.110 FTP Server – 192.168.1.9  OSI/TCP/IP MODEL COMPARISON FIVE DIFFERENT PDUS USED IN DATA ENCAPSULATION PROCESS 1. Data (Data Stream) 2. Segment 3. Packet 4. Frame 5. Bits (Bit Stream) Encapsulation Example Encapsulation is a topdown process. This process is repeated by each layer until it is sent out as a bit stream. The OSI model - divides the network access layer and the application layer of the TCP/IP model into multiple layers. The TCP/IP protocol suite does not specify which protocols to use when transmitting over a physical medium. DATA ENCAPSULATION - The form that a piece of data takes at any layer is called a protocol data unit (PDU). Segmenting Messages - the process of breaking up messages into smaller units. Multiplexing is the processes of taking multiple streams of segmented data and interleaving them together. De-Encapsulation Example Data is de-encapsulated as it moves up the stack. 2 PRIMARY BENEFITS OF SEGMENTING MESSAGES This is repeated at each layer until it is a data Increases speed - Large amounts of data can be stream that the application can process. sent over the network without tying up a communications link. Increases efficiency - Only segments which fail to reach the destination need to be retransmitted, not the entire data stream. Sequencing messages - is the process of numbering the segments so that the message may be reassembled at the destination. TCP is responsible for sequencing the individual segments. Protocol Data Units Encapsulation - is the process where protocols add their information to the data.  OPEN STANDARDS International Telecommunications Union- Telecommunication Standardization Sector (ITU-T) - Open standards encourage: defines standards for video compression, Internet Protocol interoperability Television (IPTV), and broadband communications, such as a digital subscriber line (DSL) competition innovation REFERENCE MODELS Standards organizations are: Network Model – is only a representation of a network vendor-neutral operation. The model is not the actual network. non-profit organizations The Benefits of Using a Layered Model established to develop and promote the concept of Two layered models describe network operations: open standards. Open System Interconnection (OSI) Reference Model INTERNET STANDARDS TCP/IP Reference Model Internet Society (ISOC) - Promotes the open development and evolution of internet THE OSI REFERENCE MODEL Internet Architecture Board (IAB) - Responsible for management and development of internet standards Application - Contains protocols used for process-to- process communications. Internet Engineering Task Force (IETF) - Develops, updates, and maintains internet and TCP/IP technologies Presentation - Provides for common representation of the data transferred between application layer services. Internet Research Task Force (IRTF) - Focused on long- term research related to internet and TCP/IP protocols Session - Provides services to the presentation layer and to manage data exchange. Internet Corporation for Assigned Names and Numbers (ICANN) - Coordinates IP address allocation, Transport - Defines services to segment, transfer, and the management of domain names, and assignment of reassemble the data for individual communications. other information Network - Provides services to exchange the individual Internet Assigned Numbers Authority (IANA) - pieces of data over the network. Oversees and manages IP address allocation, domain Data Link - Describes methods for exchanging data name management, and protocol identifiers for ICANN frames over a common media. Physical - Describes the means to activate, maintain, and ELECTRONIC AND COMMUNICATIONS STANDARDS de-activate physical connections. Institute of Electrical and Electronics Engineers (IEEE, pronounced “I-triple-E”) - dedicated to creating THE TCP/IP REFERENCE MODEL standards in power and energy, healthcare, telecommunications, and networking Application - Represents data to the user, plus encoding and dialog control. Electronic Industries Alliance (EIA) - develops standards relating to electrical wiring, connectors, and the Transport - Supports communication between various 19-inch racks used to mount networking equipment devices across diverse networks. Telecommunications Industry Association (TIA) - Internet - Determines the best path through the network develops communication standards in radio equipment, cellular towers, Voice over IP (VoIP) devices, satellite Network Access - Controls the hardware devices and communications, and more media that make up the network.  EVOLUTION OF PROTOCOL SUITES Internet Protocol Suite or TCP/IP- The most common protocol suite and maintained by the Internet Engineering Task Force (IETF) Open Systems Interconnection (OSI) protocols- Developed by the International Organization for Standardization (ISO) and the International Telecommunications Union (ITU) AppleTalk- Proprietary suite release by Apple Inc. Novell NetWare- Proprietary suite developed by Novell Inc. TCP/IP COMMUNICATION PROCESS A web server encapsulating and sending a web page to a client TCP/IP PROTOCOL EXAMPLE TCP/IP protocols operate at the application, transport, and internet layers. The most common network access layer LAN A client de-encapsulating the web page for the protocols are Ethernet and WLAN (wireless LAN). web browser TCP/IP is the protocol suite used by the internet and includes many protocols. An open standard protocol suite that is freely available to the public and can be used by any vendor A standards-based protocol suite that is endorsed by the networking industry and approved by a standards organization to ensure interoperability Message Timing NETWORK PROTOCOL FUNCTION Flow Control – Manages the rate of data transmission Devices use agreed-upon protocols to and defines how much information can be sent and the communicate. speed at which it can be delivered. Protocols may have may have one or functions. Response Timeout – Manages how long a device waits when it does not hear a reply from the destination. Addressing – Identifies sender and receiver Access method - Determines when someone can send a Reliability – provide guaranteed delivery message. Flow Control – ensure data flows at an efficient rate Sequencing - Uniquely labels each transmitted segment Message Delivery Option of data Unicast – one to one communication Error Detection - Determines if data became corrupted during transmission. Multicast – one to many, typically not all Application Interface - Process-to-process Broadcast – one to all communications between network applications A Note about the Node Icon PROTOCOL INTERACTION Documents may use the node icon, typically a Networks require the use of several protocols. circle, to represent all devices. Each protocol has its own function and format. Hypertext Transfer Protocol (HTTP) - Governs the way NETWORK PROTOCOL OVERVIEW a web server and a web client interact and defines content and format. Network Protocol - define a common set of rules. Transmission Control Protocol (TCP) - Manages the Can be implemented on devices in: individual conversations, Provides guaranteed deliver and Software manages flow control. Hardware Internet Protocol (IP) - Delivers messages globally from the sender to the receiver. Both Ethernet - Delivers messages from one NIC to another Protocols have their own: NIC on the same Ethernet Local Area Network (LAN). Function Format NETWORK PROTOCOL SUITES Rules Protocol Suite - A group of inter-related protocols PROTOCOL TYPE necessary to perform a communication function and sets of rules that work together to help solve a problem. Network Communications - enable two or more devices to communicate over one or more networks Higher Layers Network Security - secure data to provide authentication, Lower Layers- concerned with moving data and data integrity, and data encryption provide services to upper layers Routing - enable routers to exchange route information, compare path information, and select best path Service Discovery - used for the automatic detection of devices or services  Rule Establishment Individuals must use established rules or agreements to govern the conversation. The first message is difficult to read because it is not formatted properly. The second shows the message properly formatted. Protocols must account for the following requirements: An identified sender and receiver Common language and grammar Speed and timing of delivery Confirmation or acknowledgment requirements Switch Virtual Interface Configuration Network Protocol Requirements To configure an SVI on a switch: Common computer protocols must be in agreement and include the following requirements: Enter the interface vlan 1 command in global configuration mode. Message encoding Next assign an IPv4 address using the ip Encoding - is the process of converting address ip-address subnet-mask command. information into another acceptable form for transmission. Finally, enable the virtual interface using the no shutdown command. Decoding - is the process of converting information into another acceptable form for transmission. THE RULES Message Formatting and Encapsulation Communication Fundamentals Message formats depend on the type of message and the channel that is used to deliver the There are three elements to any communication: message. There will be a source (sender). Message Size There will be a destination (receiver). Encoding between hosts must be in an appropriate format for the medium There will be a channel (media) that provides for the path of communications to occur. Messages sent across the network are converted to bits The bits are encoded into a pattern of light, sound, Communication Protocols or electrical impulses. Protocols are the rules that communications will The destination host must decode the signals to follow. interpret the message. These rules will vary depending on the protocol.  To manually configure an IPv4 address on a Windows PC, open the Control Panel > Network Sharing Center > Change adapter settings and choose the adapter. Next right-click and select Properties to display the Local Area Connection Properties. Next, click Properties to open the Internet Protocol Version 4 (TCP/IPv4) Properties window. Then configure the IPv4 address and subnet mask information, and default gateway. IPv6 addresses are 128 bits in length and written as a string of hexadecimal values. Every four bits is represented by a single hexadecimal digit; for a total of 32 hexadecimal values. Groups of four hexadecimal digits are separated by a colon “:”. IPv6 addresses are not case-sensitive and can be written in either lowercase or uppercase. Automatic IP Address Configuration for End Devices DHCP enables automatic IPv4 address configuration for every end device that is DHCP- INTERFACES AND PORTS enabled. Types of network media include twisted-pair End devices are typically by default using DHCP for automatic IPv4 address configuration. copper cables, fiber-optic cables, coaxial cables, or wireless. To configure DHCP on a Windows PC, open the Control Panel > Network Sharing Center > Change adapter settings and choose the Manual IP Address Configuration for End Devices adapter. Next right-click and select Properties to display the Local Area Connection Properties. IPv4 address information can be entered into end devices manually, or automatically using Dynamic Next, click Properties to open the Internet Host Configuration Protocol (DHCP). Protocol Version 4 (TCP/IPv4) Properties window, then select Obtain an IP address automatically and Obtain DNS server address automatically. Alter the Running Configurations Step 3. Execute the show running- config or show startup-config command at the Reload the device using the reload command in privileged EXEC prompt. Text displayed in the privilege EXEC mode. Note: This will cause the terminal window will be placed into the chosen device to briefly go offline, leading to network file. downtime. Step 4. Disable logging in the terminal software. The figure shows how to disable logging by choosing the None session logging option If the undesired changes were saved to the startup-config, it may be necessary to clear all the configurations using the erase startup-config command in privilege EXEC mode. After erasing the startup-config, reload the device to clear the running-config file from RAM. Capture Configuration to a Text File Configuration files - can also be saved and archived to a text document. Step 1. Open terminal emulation software, such as PuTTY or Tera Term, that is already connected to a switch. Step 2. Enable logging in to the terminal software and assign a name and file location to save the log file. The figure displays that All session IP Addresses - is the primary means of enabling devices output will be captured to the file specified (i.e., to locate one another and establish end-to-end MySwitchLogs). communication on the internet. The structure of an IPv4 address is called dotted decimal notation and is represented by four decimal numbers between 0 and 255. An IPv4 subnet mask is a 32-bit value that differentiates the network portion of the address from the host portion. Coupled with the IPv4 address, the subnet mask determines to which subnet the device is a member. The default gateway address is the IP address of the router that the host will use to access remote networks, including the internet.  BASIC DEVICE CONFIGURATION Encrypt Passwords Device Names - The first configuration command on any The startup-config and running-config files display device should be to give it a unique hostname. most passwords in plaintext. Password Guidelines - All networking devices should To encrypt all plaintext passwords, use the service limit administrative access by securing privileged EXEC, password-encryption global config commands. user EXEC, and remote Telnet access with passwords. In addition, all passwords should be encrypted and legal notifications provided. Configure Passwords Securing user EXEC mode access: Use the show running-config command to verify that the passwords on the device are now First enter line console configuration mode using encrypted. the line console 0 command in global configuration mode. Next, specify the user EXEC mode password using the password password command. Finally, enable user EXEC access using the login command. Securing privileged EXEC mode access: Banner Messages - is important to warn unauthorized First enter global configuration mode. personnel from attempting to access the device. Next, use the enable secret password command To create a banner message of the day on a network device, use the banner motd # the message of the day # global config command. Securing VTY line access: The “#” in the command syntax is called the delimiting First enter line VTY configuration mode using character. It is entered before and after the message. the line vty 0 15 command in global configuration Configuration Files mode. startup-config - This is the saved configuration file that is Next, specify the VTY password using stored in NVRAM. It contains all the commands that will the password password command. be used by the device upon startup or reboot. Flash does Finally, enable VTY access using not lose its contents when the device is powered off. the login command. running-config - This is stored in Random Access Memory (RAM). It reflects the current configuration. Modifying a running configuration affects the operation of a Cisco device immediately. RAM is volatile memory. It loses all of its content when the device is powered off or restarted. To save changes made to the running configuration to the startup configuration file, use the copy running-config startup-config privileged EXEC mode command.  COMMAND STRUCTURE 2 IOS HELP FEATURES Context-sensitive help enables you to quickly find answers to these questions: Which commands are available in each command mode? Which commands start with specific characters or group of characters? Keyword – This is a specific parameter defined in Which arguments and keywords are the operating system (in the figure, ip protocols). available to particular commands? Argument - This is not predefined; it is a value or variable defined by the user (in the figure, 192.168.10.5). IOS COMMAND SYNTAX CHECK Command syntax check verifies that a valid command was entered by the user. Boldface - indicates commands and keywords that you enter literally as shown. If the interpreter cannot understand the command being entered, it will provide Italic text - indicates arguments for which you supply feedback describing what is wrong with the values. command. Square brackets [ ] - indicate an optional element (keyword or argument). Braces brackets { } - indicate a required element (keyword or argument). IOS CLI - provides hot keys and shortcuts that make Braces and vertical lines within square brackets - configuring, monitoring, and troubleshooting easier. indicate a required choice within an optional element. Spaces are used to clearly delineate parts of the command. HOT KEYS SHORTCUTS Command syntax - provides the pattern, or format, that Tab - Completes a partial command name entry. must be used when entering a command. Backspace - Erases the character to the left of the cursor. The command is ping and the user-defined argument is Left Arrow or Ctrl+B - Moves the cursor one character to the ip-address of the destination device. For the left. example, ping 10.10.10.5. Right Arrow or Ctrl+F - Moves the cursor one character to the right. Up Arrow or Ctrl+P - Recalls the commands in the history The command is traceroute and the user-defined b