Understanding IPv4 Addressing

IP Addressing

• IP is an Internet protocol functioning as the second layer in the TCP/IP model
• IP defines internet addressing, packet formats, and routing
• Devices connecting to the Internet need a physical (MAC) and a logical (Internet) address
• An IP address is a 32-bit Internet address
• Each host in the Internet is assigned a unique 32 bit IP address
• IP addresses contain a network prefix and a host suffix
• A global authority assigns a unique prefix to networks
• A local administrator assigns a unique suffix to hosts

IPv4 Address Ranges

• The IPv4 address range is from 0.0.0.0 to 255.255.255.255, totaling 2^32 addresses
• Not all IPv4 addresses are usable for hosts
• Experimental IPv4 addresses range from 240.0.0.0 to 255.255.255.254 and are reserved for research/experimentation
• Multicast IPv4 addresses range from 224.0.0.0 to 239.255.255.255
• Link-local addresses are in the range 224.0.0.0 to 224.0.0.255
• Globally scoped multicast addresses are in the range 224.0.1.0 to 238.255.255.255
• IPv4 host addresses range from 0.0.0.0 to 223.255.255.255, but many are reserved

Public vs Private IPv4 Addresses

• Private IPv4 address blocks are set aside for private networks
• Hosts not requiring Internet access can use private addresses without restriction
• Packets using private addresses shouldn't appear on the public Internet
• Private address ranges:
  • 10.0.0.0 to 10.255.255.255 (10.0.0.0/8)
  • 172.16.0.0 to 172.31.255.255 (172.16.0.0/12)
  • 192.168.0.0 to 192.168.255.255 (192.168.0.0/16)
• With Network Address Translation (NAT), hosts can "borrow" a public address to communicate
• The majority of IPv4 unicast addresses are public
• Public IP addresses are accessible from the Internet
• Addresses are sometimes designated for other special purposes

Special IPv4 Addresses

• Special IPv4 addresses cannot be assigned to hosts for various reasons
• Some special addresses can be assigned to hosts, but there are restrictions
• Within each network, the first and last IP addresses cannot be assigned to hosts
• The first address is the network address, the last address is the broadcast address
• The default route is used as a "catch-all" when a specific route is unavailable
• The entire 0.0.0.0 - 0.255.255.255 block is reserved to point to the default route
• Loopback addresses (127.0.0.0 to 127.255.255.255) allow hosts to direct traffic to themselves; 127.0.0.1 is most common
• Link-local addresses (169.254.0.0 to 169.254.255.255) can be assigned automatically
• TEST-NET addresses (192.0.2.0 to 192.0.2.255, or 192.0.2.0/24) are used for teaching/documentation

Primary IPv4 Address Classes

• IP address designers divided the IPv4 space into three classes with varying sizes
• The three IPv4 address classes are A, B, and C
• Each class fixes the boundary between network prefix and host number
• Class A starts with 0
• Class B starts with 10
• Class C starts with 110
• Class D starts with 1110 for multicast address
• Class E starts with 1111 and is reserved for future use

IPv4 Address Classes Details

• Class A has an 8-bit network prefix prefixed with a 0, followed by a 24-bit host number
• Class A can define up to 126 (2^7-2) /8 networks
• All zeros (00000000) is the default route, and 127 is reserved for the "loopback" (01111111)
• Each Class A network supports 16,777,214 (2^24 - 2) hosts
• IPV4 address space consists of 4,294,967,296 addresses
• Class A's addresses represent 50% of the IPv4 unicast address space
• Class B uses a 16-bit network prefix starting with 10
• Class B has a 14 bit network number & 16 bit host number
• Maximum Class B networks defined is 16,384 (2^14)
• Class B supports 65,534 (2^16-2) hosts per network
• The individual address count in Class B is 1,073,741,842 (2^30), representing 25% of the IPv4 unicast space
• Each Class C network address contains a 24-bit network prefix
• Class C networks start with 110 then a 21-bit network number.
• Class C supports 2,097,152 (2^21) networks with 254 hosts per network (2^8-2)
• The number of Class C individual addresses: 536,870,912 (2^29), which is 12.5% of the total IPv4 unicast space
• Class D addresses start with 1110 for research and multicast
• Class E addresses start with 1111, and is reserved

Dotted Decimal Notation

• Dotted decimal notation makes Internet addresses easier to read and write
• This notation serves as shorthand for IP addresses
• It avoids binary for humans
• Each byte is represented in decimal, separated by dots
• Four decimal values per 32-bit IP address

Dotted Decimal Notation Ranges

• A (/8 prefix): 1.0.0.0 through 126.255.255.255
• B (/16 prefix): 128.0.0.0 through 191.255.255.255
• C (/24 prefix): 192.0.0.0 through 223.255.255.255

Problems with IPv4 Addressing

• IPv4 address space is being exhausted
• There is an increasing need to route traffic between more and more networks
• Addresses are assigned without considering the actual need
• There is a lack of a network class addressing to support medium size organizations, /24 only supports only 254 hosts, while /16 supports 65,534

Subnetting

• Subnetting is dividing a Class A, B, or C network into smaller pieces
• Subnetting was invented in 1985
• Extend address space/prevent exhaustion, control routing table growth, & minimize requests to Internet
• Goal: assign addresses to every new network in an organization
• Subnetting supports a three-level hierarchy, unlike the two-level classful system
• Two-level: Network prefix/Host number
• Three-level: Network prefix/Subnet number/Host number

Benefits of Subnetting

• Subnetting prevents the global Internet routing table does from growing
• Subnetting provides the flexibility of adding subnets without getting a new network number from the Internet
• Internal route flapping doesn't affect the global Internet routing table

Extended Network Prefix

• Extended network prefix is composed of the classful network prefix and subnet number
• Internet routers only use the network prefix of destination addresses
• Routers in subnetted environments use the extended network prefix to route traffic
• IP address = 130.5.5.25/24 (24 bit extended network prefix)

Subnet Mask

• Subnet masks identify the bits designate network address and host address
• Accompanies IP addresses as a 32-bit binary value
• It identifies the Prefix/Suffix boundary
• 1 bits cover prefix
• 0 bits cover suffix
• Default subnet masks: Class A = 255.0.0.0, Class B = 255.255.0.0, Class C = 255.255.255.0

Subnet Design Considerations

• Key points when designing subnets:
  • How many total subnets does the organization need today?
  • How many total subnets will the organization need in the future?
  • How many hosts are on the organization's largest subnet today?
  • How many hosts will there be on the organization's largest subnet in the future?
• Take the maximum number of subnets required and round up to the nearest power of two
• Ensure enough host addresses for the largest subnet.

Subnet Example

• An organization with 193.1.1.0/24 needs six subnets, with the largest supporting 25 hosts
• Solve for the extended network prefix, subnet mask, subnets, and hosts
• 2^3 = 8 subnets, allowing (2) future subnets, and 2^5 = 32 hosts
• Usable host addresses is(2^5)-2= 30 hosts, 193.1.1.0/24 is a Class C at /24.
• 193.1.1.0 = 11000001.00000001.00000001.00000000 /24
• 193.1.1.0 = 11000001.00000001.00000001.00000000 /27 E.N.P, and 255.255.255.224= 11111111.11111111.11111111.11100000/27.

Subnet Number Definition

• A binary value is assigned for each subnetwork to be numbered sequentially from 0 through 7
• First subnet number is 000= 0
• Eight sequential binary subnet numbers are assigned to subnets with range from: 000, 001, 010, 011, 100, 101, 110 to 111=7
• The complete series of base networks starts as
• 11000001.00000001.00000001.00000000= 193.1.1.0/24 goes to
• 11000001.00000001.00000001.00000000=193.1.1.0/27
• Subnet#1's host equals a multiple of subnet # 1 (32 in this case) 11000001.00000001.00000001.00100000 =193.1.1.32/27

Host Addresses per Subnet

• The host number field of IP addresses can't contain all zero bits and all one bits
• All zeros identify the base network or subnet
• All ones represent the broadcast address for the subnet
• Subnet #1's Valid host addresses equals the block (2 hosts ^ 5 hosts)-2 hosts
• Host1 on the Subnet #1 : 11000001.00000001.00000001.00100001 = 193.1.1.33/27
• Host2 on the Subnet #2: 11000001.00000001.00000001.00100010 = 193.1.1.34/27
• Host3 on the Subnet #3: 11000001.00000001.00000001.00100011 = 193.1.1.35/27
• Host4 on the Subnet #4: 11000001.00000001.00000001.00100100 = 193.1.1.36/27
• Host5 on the Subnet #5: 11000001.00000001.00000001.00100101 = 193.1.1.37/27
• Host6 on the Subnet #6: 11000001.00000001.00000001.00100110 = 2.93.1.1.38/27

VLSM (Variable Length Subnet Mask)

• VLSM is subnetting repeated multiple times to further divide a network
• VLSM creates a hierarchy of sub networks with different sizes
• VLSM allows an organization to match the size of subnetworks to their requirements
• Consider this company with address 201.45.22.0/24 for 6 subnets. The breakdown is S1, S2, S3, S4 subnets each have 10 hosts, S5 subnet has 60 hosts while S6 has 100 hosts.
• First allocate one bit for subnet and have only 7 remaining bits for hosts
• As such, you can only have 2 subnets with a maximum of 126 hosts with subnets: 201.45.22.0/25 and 201.45.22.128/25.
• Re-addressing the first subnet for S6 with 100 hosts using.
• The subnets become re-addressed by 201.45.22.128/25 to to create new 2 subnets each with maximum 62 host machines.
• With the new S5 and S6 have subnets with the addresses 201.45.22.128/26, 201.45.22.192/26.
• S1, S2, S3 and S4 get readdressed the by 201.45.22.192/26 be further subnet it into 4 subnets each with 14 hosts: 201.45.22.192/28, 201.45.22.208/28, 201.45.22.224/28 and 201.45.22.240/28

Final-Step VLSM

• You should subnet only for the WAN links
• WAN links only really require two addresses.
• For two addresses: borrow more 2 bits by using /30 mask.
• With the addresses set and configured as: Subnet 0: 192.168.15.128 /30, host address 129 to 130, Subnet 1: 192.168.15.132/30, host address 133 to 134, Subnet 2: 192.168.15.136/30 host address 137 to 138
• As seen, VLSM maximizes addressing while minimizing waste

Planning IP Addressing Hierarchy

• IP Addressing Hierarchy influences network routing efficiency
• IP addressing hierarchy reduces network routing overhead
• Route Summarization (route aggregation/super netting) is vital for Internet operation
• Classless Inter-Domain Routing (CIDR) was to handle address exhaustion and routing table growth
• With CIDR, blocks of multiple addresses (Class C blocks) can be combined to create larger sets of classless addresses
• The goal of route summarization is to reduce route entries on core routers

Route Summarization Rules

• Subnetting is dividing networks into smaller sub-networks
• Super netting: summarized sub networks into a single one
• First you identify the smallesrt & largest IP addresses
• Then determine Group Size Increment in relevant Octet of both IP's
• Other rules:

1. Find the common bits
2. Represent common bits with 1 and uncommon with 0
3. Calculate block size
4. Represent network with block size
5. Find your match

Route Summarization Examples

• Find the common bits to summarize route (One Route only), the list is:
  • 10.10.10.0/28
  • 10.10.10.16/28
  • 10.10.10.32/28
  • 10.10.10.48/28
  • 10.10.10.64/28
  • 10.10.10.80/28
  • 10.10.10.96/28
  • 10.10.10.112/28
• Answer to question by the list: The single network is 10.10.10.0/25
• Find the common bits to summarize route. (One Route only), the list is:
  • 10.10.17.0/24
  • 10.10.18.0/24
  • 10.10.19.0/24
  • 10.10.20.0/24
  • 10.10.21.0/24
  • 10.10.22.0/24
• Answer to question by the list: The single network is 10.10.16.0/21

Router Addressing

• Routers perform route summarization to aggregate networks
• A router has the following networks: 192.168.168.0/24,192.168.169.0/24,192.168.170.0/24 Route) only),192.168.171.0/24, 192.168.172.0/24, , 192.168.173.0/24, 192.168.174.0/24 192.168.175.0/24

Network Sizing Factors

• Determine the IP addressing plan by determining the size with subnets/hosts
• Gather these data using the questions below
• How many locations make up the network?
• Determine number and type of locations.
• How many devices in each location need addresses?
• Determine how many devices need addressing
• End systems, router interfaces, switches, and firewalls

Individual Addressing and Switch

• Determine the amount of addressing requirements
• Designer must account dynamic, static, and private systems/addresses
• Estimate subnet size based on ports and network switch deployment
• For 48-port switches, 64 host addresses will suffice assuming one device per port
• Determine many bits you need

IP Assignment Methods

• Answer the questions below before selecting an IP address assignment method
• How many devices need an IP address?
• Which devices require static IP address assignment?
• Is IP address renumbering expected in the future?
• Is the administrator required to track devices and their IP addresses?
• Are configurations of default gateways or name servers necessary?
• Are there any availability or security issues?

Static vs Dynamic IP Assignment

• Static assignment involves assigning an IP address(es) to a computer node
• Dynamic assignment dynamically assigns addresses to the end systems
• Static is great for static systems, but a bad choice for dynamic ones
• Static is okay for a small system, whereas Dynamic is great for a larger one
• Node type: Network routers or switches mostly have static IP assignment
• End-user devices like local PC's often have dynamically addressed hosts.

System Considerations

• With more than 30 end nodes ,the IP dynamic address assignment is best
• Static is preferable in small, less complex type networks
• If renumbering is to happen and systems undergo end reconfiguration, dynamic assignment is best
• DHCP (Dynamic Host Configuration Protocol) will make this process better too
• Dynamic address assigned systems can allow traffic from anyone

Parameters

• DHCP is easiest when additional parameters are needed
• Parameters are only assigned to the server and can be sent to the clients
• Static IP addresses are often available from servers, whereas DHCP servers may go down
• Use a redundant DHCP server
• With dynamic IP assignment, anyone connecting to the network can acquire a valid IP address
• Static IP causes a security risk, versus dynamic which may cause that as well

DHCP Operation

• DHCP provides dynamic IPv4 address allocation for hosts
• DHCP clients send a DHCPDISCOVER broadcast message to find a DHCP server
• A DHCP server replies to the DHCP client with DHCP offer message
• The DHCP server provides the configurations parameters including the IP, MAC address, domain name, default gateway.
• The DCHCP cient will then proceed to reply this with DHCPREQUEST, to the server
• Step4: The DHCP server will proceed to assign the IP once by returning back DHCBACK message

IPv6 Considerations

• Development in 1990s due to IPv4 running out
• IPv6 protocol is not a layer 3 protocol, as it it's very own protocol
• IPv6 is 128 bit hierarchical, uses hexadecimal
• IPv4 Address ranges is (2^32 = 4,294,967,296 addresses)
• IPv6 Address ranges is (2^128 addresses =) = 340,282,366,920,938,463,463,374,607,431,768,211,456(or)340 trillion, trillion, trillion

IPv6 Introduction

• IP version 6 (IPv6), developed by IETF, is the latest IP revision
• Reasons it exists:
  • IPv4 is too limited even with inter-domain routing
  • IPv4 lacksof direct security and QoS
  • IPv4 lacks a configuration to support globally unique IP address
  • Mobility issues with v4
• IPv6 Features:
  • Larger Address space
  • Simplified Header
  • Globally unique and hierarchical address
  • Allows auto network interface configurations
  • Built-in authentication and encryption
  • Provides Mobility and Compatability
  • Has faster forwarding/routing

IPv6 Address Considerations

• There are addressing modes and formats for this protocol
• Lacks broadcast addresses but Anycast addresses present
• IPv6 addressing modes:
  • Unicast, addresses the one host
  • Multicast, addresses the multiple hosts
  • Anycast: addresses to groups for specific hosts/nodes
• IPv6 addresses are made of 128 bits.
• Divided into eight 16-bit blocks.
• Each block is then converted into 4-digit Hexadecimal numbers separated by colon symbols -2001:0000:3238:DFE1:0063:0000:0000:FEFB

IPv6 Headers

• IPv6 addresses are only two times bigger than IPv4.
• v6 headers are madeFixed Header (req) + Optional headers)
• All IPv6's have Fixed Headers, in comparison.

IPv4/IPv6 Transition

• Transition will still take time due to costs in infrastructure
• IPv4/IPv6 must coexist with one of the following
• Dual-Stacking: With IPv4 stacks with IPv6 stacks ,each stacks on nodes with both V4, & v6
• Tunneling: Use encapsulation of IPv6 traffic, packets transfer over across old IPv4
• Translation: Will translate the old IPs (v4) into newer IPv6, facilitates communications
• Provides legacy, for all for equipments for IPv6, to provide deployment for old, old and new systems

Name Resolution

• Names are easier to remember than IP addresses
• Questions regarding Static vs. Dynamic Name Resolution: -How many hosts require name resolution? -Are applications that depend on name resolution present? -Is the network isolated or connected to the Internet? -If the network is isolated, how frequently are new hosts added and how frequently do names change?
• Local name databases are known as _______.
• Discuss the various DNS (Domain Name Server) options/mechanisms for naming convention.
• DNS also handles website URL's with DNS system through resolution