IP AddressingNGN Faculty ALTTC,Ghaziabad INDIA

What is an IP address?Each host on a TCP/IP network is uniquely identified at the IP layer with an address.An Internet Protocol (IP) address specifies the location of a host or client on the Internet.The IP address is also known as Protocol addressThe IPv4 address is 32 bits long

IPv4 Address SchemeWhat the Internet machines see an IP address? 11001010000011100100000000000001For human understanding the 32 bits of IP address are separated into 4 bytes of 8 binary digitsEach binary byte is converted into decimal and is separated by a dot hence also known as Dotted Decimal NotationHow we see an IP address? 202.14.64.1

IPv4 Address Scheme

In decimal the address range is 0.0.0.0 to 255.255.255.255The IP address is of the form 8 Bits8 Bits8 Bits8 Bits172 . 16 . 122 . 204

IPv4 Address SchemeTwo types of addressing schemes for IPv4ClassfulClassless Classful Original style of addressing based on first few bits of the address.Generally used in customer sites.ClasslessA new type of addressing that disregards the class bit of an address and applies a variable prefix (mask) to determine the network number.

IPv4 Address SchemeThere are five classes of addresses A, B, C, D & E. A, B & C classes are used to represent host and network address.Class D is a special type of address used for multicasting.Class E is reserved for experimental use.

IPv4 Address classesHN=Network number assigned by IR.H=Host number assigned by network administrator.

Network Address MaskClass-A Address00001010.00001010.01000000.00001001Natural or Default Mask is /811111111.00000000.00000000.00000000255.0.0.0Class-B Address10001010.00001110.01010000.00000001Natural or Default Mask is /1611111111.11111111.00000000.00000000255.255.0.0

Network Address MaskClass-C Address11001010.00001100.01000000.10000001Natural or Default Mask is /2411111111.11111111.11111111.00000000255.255.255.0

Identifying a class of addressAddress IdentifierNetwork AddressHost Address

Class-A address (Networks)Number of Networks = 27 i.e.128 (0-127)Network ID 0 is not used.Network ID 127 is reserved for loop back and is used for internal testing.Number of Networks = 126Network IDs = 1-126

Class-A address (Hosts)Number of Hosts=224=16777216No Host ID can have all zeros i.e. 0.0.0 and specifies network address.No Host ID can have all ones i.e. 255.255.255 and specifies the broadcast address.Number of Hosts per network= 224 -2=16777214

IPv4 addressAll 0s in the host ID indicates the network itself.All 1s in the host ID indicates the broadcast address.

Class-B addressNumber of Networks = 214 i.e.16384Number of Hosts = 216 i.e. 65,536 (0-65,535)No Host ID can have all zeros i.e. 0.0 and specifies network address.No Host ID can have all ones i.e. 255.255 and specifies the broadcast address.Number of Hosts per network= 216 -2=65534

Class-C addressNumber of Networks = 221 i.e. 2097152Number of Hosts = 28 i.e. 256 (0-255)No Host ID can have all zeros i.e. 00000000 and specifies network address.No Host ID can have all ones i.e. 11111111 and specifies the broadcast address.Number of Hosts = 28-2 = 254

Class-D & E addressesClass D are special addresses are known as multicast addressesThis address is assigned to a group of networks and not to represent a unique addressThis address is used to send IP datagrams to a group but not to all the hosts on the networkThis address is also used to address router update messages

IP Address Bit Patterns

Address space utilisation

Networks Vs HostsIn Classless environment we can have 232=4294967296 HostsClassNetworksHosts/NetworkA12616777214B1638465354C2097152254Having 16777214 hosts for Class-A and 254 hosts for Class-C were not working well

SubnettingChopping up of a network into a number of smaller networks is called subnetting.Allows to assign some of the bits, normally used by the host portion of the address, to the network portion of the address.The format of subnetted IP address would be Efficiently uses the full network address.Subnet is a real network under a network.Any of the classes can be subnetted.

Subnetting (1 Bit)0000000 - 00000001 - 10000010 - 2 . . . .1111110 - 1261111111 - 127

Subnetting (2 Bits)000000 - 0000001 - 1 000010 - 2 . . . .111110 - 62111111 - 63

Subnetting (8 Bits)Default / Natural Mask:172.16.H.H /168 bit Subnetting:172.16.N.H /24

Identifying Network AddressFive bits of subnettingSubnet address:201.222.5.120 (0+64+32+16+8)Host Number :1

Variable Length Subnet MaskSubnetting creates subnets with equal number of hosts, in a network.The number of bits subnetted i.e. the length of subnet mask will be same for all the subnets.To cop up with the variable number of hosts in subnets, in a network, number subnetted bits i.e. the length of subnet mask for the subnets will also vary.The method of achieving subnetting, with variable length of subnet mask, is known as Variable Length Subnet Mask.

Variable Length Subnet Mask= 27 = 128= 26 = 64= 24 = 16= 24 = 16= 23 = 8= 22 = 4= 22 = 4= 22 = 4E- 100HA- 50HC- 14HB- 13H D- 6H SL1SL2SL3

Variable Length Subnet Mask= 27 = 128= 26 = 64= 24 = 16= 24 = 16= 23 = 8= 22 = 4= 22 = 4= 22 = 4E- 100HA- 50HC- 14HB- 13H D- 6H SL1SL2SL3E - 202.195.32.0 0000000A - 202.195.32.10 000000C - 202.195.32.1100 0000B - 202.195.32.1101 0000D - 202.195.32.11100 000SL1- 202.195.32.111010 00SL2- 202.195.32.111011 00SL3- 202.195.32.111100 00

Variable Length Subnet MaskN/W N/W Address E - 202.195.32.0 0000000 202.195.32.0 A - 202.195.32.10 000000 202.195.32.128 C - 202.195.32.1100 0000 202.195.32.192 B - 202.195.32.1101 0000 202.195.32.208 D - 202.195.32.11100 000 202.195.32.224 SL1 - 202.195.32.111010 00 202.195.32.232 SL2 - 202.195.32.111011 00 202.195.32.236 SL3 - 202.195.32.111100 00 202.195.32.240 Network Address:Set all host bits to zeroCalculate the binary value of last byte

Variable Length Subnet MaskN/W B/C Address E - 202.195.32.0 1111111 202.195.32.127 A - 202.195.32.10 111111 202.195.32.191 C - 202.195.32.1100 1111 202.195.32.207 B - 202.195.32.1101 1111 202.195.32.223 D - 202.195.32.11100 111 202.195.32.231SL1 - 202.195.32.111010 11 202.195.32.235SL2 - 202.195.32.111011 11 202.195.32.239 SL3 - 202.195.32.111100 11 202.195.32.243Broadcast Address:Set all host bits to oneCalculate the binary value of last byte

Variable Length Subnet MaskN/W N/W Address B/C Address E - 202.195.32.0 202.195.32.127A - 202.195.32.128 202.195.32.191 C - 202.195.32.192 202.195.32.207B - 202.195.32.208 202.195.32.223D - 202.195.32.224 202.195.32.231SL1 - 202.195.32.232 202.195.32.235SL2 - 202.195.32.236 202.195.32.239 SL3 - 202.195.32.240 202.195.32.243N/W IP Address RangeE-202.195.32.1 202.195.32.126A-202.195.32.129 202.195.32.190C-202.195.32.193 202.195.32.206B-202.195.32.209 202.195.32.222D-202.195.32.225 202.195.32.230SL1-202.195.32.233 202.195.32.234SL2- 202.195.32.237 202.195.32.238SL3- 202.195.32.241 202.195.32.242

CIDRClassless Inter Domain RoutingPronounced as - ciderAlso known by the name supernettingRFC 1519Helps in reducing number of route table entries192.168.0.0/24192.168.1.0/24192.168.0.0/22192.168.2.0/24192.168.3.0/24

Without CIDR198.32.1.0198.32.3.0198.32.2.0198.33.1.0198.33.1.0198.32.1.0198.32.2.0198.32.3.0

198.0.0.0/8198.33.0.0/16198.32.0.0/16With CIDR

CIDRInitially IP addresses were arbitrarily handed out without regard to geographic location and were overtaxing the Internet routing tablesClass A stopped being handed out and Class-B was exhaustedWith the remaining Class-C addresses the whole world has been divided into 4 zonesEach zone is given a portion of Class-C addresses194.0.0.0 to 195.255.255.255 (Europe)198.0.0.0 to 199.255.255.255 (North America)200.0.0.0 to 201.255.255.255 (C&S.America)202.0.0.0 to 203.255.255.255 (Asia & the Pacific)

CIDREach zone is given about (2x224) 32 million addresses to allocateAnother (20x224) 320 million Class-C addresses 204.0.0.0 to 223.255.255.255 are reserved for future.32 million address entries have been compressed to one router table entry.Any route outside Europe that gets packet addressed to 194.0.0.0 to 195.255.255.255 can just send it to Standard European Gateway.Once a packet gets to Europe (2x28x28) 131072 network entries are needed.

IP V6

The IPV6 address will be likeX:X:X:X:X:X:X:X

IPv6 Address Representation..The leading zeros of a 16 bits section between two colons can be omittedTrailing zeros cant be omitted1080:0000:0000:0000:0008:0800:200C:417A may be simplified to 1080:0:0:0:8:800:200C:417A If long strings of zeros appear in an address, a double colon may be used to indicate multiple groups of 16 bits of zeros1080:0:0:0:8:800:200C:417A may be further simplified to 1080::8:800:200C:417A

IPv6 Address RepresentationThe use of double colon is restricted to appearing only once in an addressFEDC:0:0:0:8123:0:0:417A may be written as FEDC::8123:0:0:417A or FEDC:0:0:0:8123::417A0:0:0:0:0:0:0:1 may be simplified as ::1

Addressing ArchitectureFirst few bits of IP address is called Type/Format prefixIt is of Variable-Length in coded form

Loopback AddressThe address 0:0:0:0:0:0:0:1 (0::1) or (::1) is defined as loopback addressUsed by a node to send packet to itself

Unspecified addressThe address 0:0:0:0:0:0:0:0 (0::0) or (::) is defined as unspecified addressMay never be assigned to any node

IPv4-Compatible IPv6 AddressA transition address for IPv4/IPv6 transition networksUsed when two IPv6 devices, hosts or routers, need to communicate via an IPv4 routing infrastructureThe process is called automatic tunneling

IPv4-Mapped IPv6 AddressA transition address for IPv4/IPv6 transition networksUsed by IPv4-only nodes that do not support IPv6An IPv6 host would use an IPv4-mapped IPv6 address to communicate with another host which supports only IPv4