TCP/IP Address Overview

• End stations communicate seamlessly with servers or other stations

• Each node uses a unique 32 bit IP address

IP Datagrams

• Include a unique source IP address and Destination IP address

• IP addresses identify the source and destination network and host

Internetwork

• Each company listed on the internetwork must be reached before an individual host within that company can be contacted

• Host populating that network share the same network bits but are identified by a uniqueness of the remaining bits

IP Address

• 32 bits in length

• Contains two parts– Network number– Host number

• Binary in nature

• Expressed in a format that can be read by the human eye

IP Address Sections

• Broken into 4 sections of 8 bits called octets

• Each octet is converted to decimal format and is separated by dots

• 255.255.255.255

11111111|11111111|11111111|11111111

• 172.16.122.204

10101100|00010000|01111010|11001100

Octets

• Minimum octet value is 0 – all zeros

• Maximum octet value is 255 – all ones

Address Allocation

• Addresses are allocated by a central authority, the American Registry of Internetwork Numbers (ARIN)

• See www.arin.net for more information

Early IP Addresses

• Early IP addresses did not use classes because there weren’t very many networks

• Now a class system is necessary to increase the number of available IP addresses

IP Address Classes

8 Bits 8 Bits 8 Bits 8 Bits

Class A Network Host Host Host

Class B Network Network Host Host

Class C Network Network Network Host

Class D Multicast

Class E Research

Analysis of Class System

• Class A networks have only 8 network bits and 24 host field bits

• Therefore, there are few Class A networks• There are more Class B networks and even more

yet Class C networks each with fewer hosts• Class system allows addresses to be assigned

based on the size of the network• There are many more small networks than there

are large networks

Address ClassificationBits: 1 8 9 16 17 24 25 32

Class A: 0NNNNNNN Host Host Host

Range(1–126)

Bits: 1 8 9 16 17 24 25 32

Class B: 10NNNNNN Network Host Host

Range(128–191)

Bits: 1 9 16 17 24 25 32

Class C 110NNNNN Network Network Host

Range(192–223)

Class Ranges

Class A Class B Class C

Starts with:

0 10 110

Range: 1.0.0.0 to

126.0.0.0

128.0.0.0 to

191.255.0.0

192.0.0.0 to

223.255.255.0

Networks: 127 (1-126)

127 is reserved

16,384 2,097,152

Hosts: 16,777,216 – 2 65,536 – 2 256 – 2

Class D – Multicast Addresses

Bits: 1 8 9 16 17 24 25 32

Class D: 1110MMMM Multicast Grp

Multicast Grp

Multicast Grp

Range(224–239)

Includes the following range of network numbers: 224.0.0.0 to 239.255.255.255

Class E – Research Addresses

Bits: 1 8 9 16 17 24 25 32

Class E: 11110RRR Research Grp Research Grp Research Grp

Range(240–247)

Includes the following range of network numbers: 240.0.0.0 to 247.255.255.255

Reserved Addresses

• RFC 1918 defines the following as reserved addresses:

• 10.0.0.0 through 10.255.255.255

• 172.16.0.0 through 172.31.255.255

• 192.168.0.0 through 192.168.255.255

Host Addresses

10.250.8.11Router

10.6.24.2

E1

10.180.30.118

172.16.2.100

E0

172.16.2.1

172.16.12.12

172.16.3.10

10.1.1.1

Routing Table

Network Interface

172.16.0.0

E0

10.0.0.0 E1

Host Address Conventions

• Host address of 0 means this network or wire address, i.e., 172.16.0.0

• Router uses network address to identify subnet

• Routing table contains entries for each network

• All 1s is a broadcast address.• Number of addresses in network is 2N – 2

Default Subnet Masks

Class Format Default Subnet Mask

A network.node.node.node 255.0.0.0

B network.network.node.node 255.255.0.0

C network.network.network.node

255.255.255.0

Subnet Example

172.16.3.100Router

172.16.3.1

E1

172.16.3.150

172.16.2.200

E0

172.16.2.1

172.16.2.160

172.16.2.2

172.16.3.5

Routing Table

Network Interface

172.16.2.0

E0

172.16.3.0

E1

Subnet Mask Example

network network host host

IP Address 172 16 0 0

network network host host

Default Mask 255 255 0 0

written as: /16

network network subnet host

Subnet Mask 255 255 255 0

written as: /24

Subnet Mask Numbering

• 1 for network bits

• 1 for subnet bits

• 0 for host bits

Methods of Representation

• Dotted Decimal – 172.16.0.0 255.255.0.0

• Bit Count – 172.16.0.0/16

• Hexadecimal – 172.16.0.0xFFFF0000

Possible Subnet Mask Values

1 0 0 0 0 0 0 0 = 128

1 1 0 0 0 0 0 0 = 192

1 1 1 0 0 0 0 0 = 224

1 1 1 1 0 0 0 0 = 240

1 1 1 1 1 0 0 0 = 248

1 1 1 1 1 1 0 0 = 252

1 1 1 1 1 1 1 0 = 254

1 1 1 1 1 1 1 1 = 255

Calculating Network Number – No Subnet Bits /16

network network host host

172.16.2.160 10101100

00010000

00000010

10100000

255.255.0.0 11111111

11111111

00000000

00000000

10101100

00010000

00000000

00000000

Network Number

172 16 0 0

Calculating Subnet Number – 8 Subnet Bits /24

network network host host

172.16.2.160 10101100

00010000

00000010

10100000

255.255.0.0 11111111

11111111

11111111

00000000

10101100

00010000

00000010

00000000

Subnet Number 172 16 2 0

Calculating Subnet Number – 10 Subnet Bits /26

network network subnet host

172.16.2.160 10101100

00010000

000000 10

100000

255.255.0.0 11111111

11111111

111111 11

000000

10101100

00010000

000000 10

000000

Subnet Number 172 16 2 128

Class B Broadcasts

From 172.16.1.12

• Local to Subnet 1 – 255.255.255.255

• Specific to Subnet 3 – 172.16.3.255

• To All Subnets – 172.16.255.255

Defining Class B Subnet – /26

172.16.2.160 10101100

00010000

00000010 10

100000

host

255.255.255.192

11111111

11111111

11111111 11

000000

mask

172.16.2.128 10101100

00010000

00000010 10

000000

subnet

172.16.2.191 10101100

00010000

00000010 10

111111

broadcast

171.16.2.129 10101100

00010000

00000010 10

000001

first

171.16.2.190 10101100

00010000

00000010 10

111110

last

Defining Class B Subnet – /24

172.16.2.121 10101100

00010000

00000010

10100000

host

255.255.255.0 11111111

11111111

11111111

00000000

mask

172.16.2.0 10101100

00010000

00000010

00000000

subnet

172.16.2.255 10101100

00010000

00000010

11111111

broadcast

171.16.2.1 10101100

00010000

00000010

00000001

first

171.16.2.254 10101100

00010000

00000010

11111110

last

Possible Class B Combinationsbits subnet mask subnet

shosts

2 255.255.192.0 2 16382

3 255.255.224.0 6 8190

4 255.255.240.0 14 4094

5 255.255.248.0 30 2046

6 255.255.252.0 62 1022

7 255.255.254.0 126 510

8 255.255.255.0 254 254

9 255.255.255.128 510 126

10 255.255.255.192 1022 62

11 255.255.255.224 2046 30

12 255.255.255.240 4094 14

13 255.255.255.248 8190 6

14 255.255.255.252 16382 2

Network Design

• Class C Network with address 172.16.2.121

• Supports at least 20 subnets – 5 bits

• Each Subnet has at least 5 hosts – 3 bits

Class C Network Specifications – /29

network network network subnet host

192.168.5.121 11000000

10101000

00000101

01111 001 host

255.255.255.248

11111111

11111111

11111111

11111 000 mask

192.168.5.120 11000000

10101000

00000101

01111 000 subnet

192.168.5.127 11000000

10101000

00000101

01111 111 broadcast

192.168.5.121 11000000

10101000

00000101

01111 001 first

192.168.5.126 11000000

10101000

00000101

01111 110 last

Possible Class C Combinations

bits subnet mask subnets

hosts

2 255.255.255.192 2 62

3 255.255.255.224 6 30

4 255.255.255.240 14 14

5 255.255.255.248 30 6

6 255.255.255.252 62 2

Configuring IP Addresses

• Assign logical network address and default gateway to a switch

• Assign logical network address to a router interface

• Specify the subnet mask format• Assign host names to IP addresses• Define name servers• Display a list of host names and addresses

Logical Network Address – Switch

Use ip address global command to establish a logical network on a series 1900 switch:

Switch(confid)#ip address ip-address subnet mask

– ip-address is a 32-bit dotted-decimal number

– subnet-mask is a 32-bit dotted-decimal number used to identify the network/subnet or host

Default Gateway

Use the ip default-gateway command to define a default gateway on a switch such as the Catalyst 1900 series

Switch(config)#ip default-gateway ip-address

Logical Network Address – Router

Use the router ip address interface configuration command to establish a logical network address on a router interface

Router(config-if)#ip address ip-address subnet-mask

Subnet Mask Format• show commands display an IP address and subnet mask in dotted

decimal, bit count or hexadecimal notation. • Subnet masks are displayed in dotted decimal notation by default• To specify a format for the current session:

Router#term ip netmask-format {bitcount|decimal|hexadecimal}

• To specify a format for a specific line:

Router(config-line)#ip netmask-format {bitcount|decimal|hexadecimal}

• Although you can display subnet masks in bitcount, decimal, and hexadecimal formats, you can only configure an IP and subnet mask with the dotted decimal format

Assigning Host Names

• Cisco IOS software maintains a table of host names and their corresponding address that is called the host name-to-address mapping

• Higher-layer protocols such as Telnet might use host names to identify network devices (hosts)

• Host names and IP addresses can be associated through either static or dynamic means

Manual Host Name Examples

• The following manually assigns a hostname:

Router(config-line)#ip host name [tcp-port-number] address [address]

• Name is the name that describes the host location

• tcp-port-number is an optional TCP number that identifies the TCP port to use with EXEC connect or Telnet command

• address is the IP address where the name can be reached. Each device can have up to eight different addresses to identify a host

Host Name Examples

• Example 1 – associates the name Norine with two IP addresses. The router will attempt to connect with 172.16.3.1 first when Telnetting to Norine

• Router(config-line)#ip host Norine 172.16.3.1 192.168.3.1

• Example 2 – associates the name Roger with 172.16.3.1

• Router(config-line)#ip host Roger 172.16.3.1

Defining Name Servers

• The ip name-server command defines which hosts can provide name service

• A maximum of six IP addresses can be specified:

Router(config)#ip name-server server address [server address]

Domain LookupRouter(config)#ip domain-lookup

Router(config)#end

Router#pat

Translating “pat” … domain server (255.255.255.255)

% Unknown command or computer name, or unable to find computer address

Router#config t

Router(config)#no ip domain-lookup

Router(config)#end

Router#pat

Translating “pat”

% Unknown command or computer name, or unable to find computer address

Router#

Displaying Host Names and AddressesRouter#show hosts

Default domain is not set

Name/address lookup uses domain service

Name servers are 255.255.255.255

Host Flags Age Type Address(es)

Norine (perm, OK) 0 IP 172.16.100.100

Roger (perm, OK) 0 IP 172.16.100.101

Frank (perm, OK) 0 IP 172.16.200.200

Bob (Perm, OK) 0 IP 172.16.200.201

Show Hosts FieldsShow hosts Command Field Description

Host Names of learned hosts

Flags How host info was learned and status

perm Manually configured in static host table

temp Acquired from DNS use

OK Entry is current

Ex Entry has aged out (expired)

Age Time measured in hours since software referred to entry

Type Protocol field

Address(es) Logical addresses associated with name of host

Inter-VLAN Routing

• Routers can be used to interconnect networks with IP

• In a switched VLAN, packets are switched only between ports in the same “broadcast domain”

• Inter VLAN communication cannot occur without a network layer device (router)

• Router attached to a core switch is called a “router on a stick”

VLAN Routing Using ISL

10.2.2.2

Fast

E0/0

ISLRouter on a Stick

10.1.1.2

VLAN 2VlAN 1

Switch

VLAN Routing Requirements

• Router must know how to reach all interconnected VLANs

• Each end device must be addressed with a network layer address such as an IP address

• The router already knows about directly connected networks. It must learn routes to networks that are not directly connected

• There must be a separate physical connection for each VLAN or trunking must be enabled on a single physical connection (Chapter 8)

ISL Router Configurationinterface fastethernet 0/0 no ip address!interface fastethernet 0/0.1 ip address 10.1.1.1 255.255.255.0 encapsulation isl 1interface fastethernet 0/0.2 ip address 10.2.2.2 255.255.255.0 encapsulation isl 2

To Configure “Router on a Stick”

• Enable ISL on the switch port connecting to the router

• Enable ISL encapsulation on the router’s Fast Ethernet subinterface

• Assign a network layer address to each subinterface

Note: the router must sometimes learn routes either statically or dynamically (Chapter 8)

Routing Across a WAN

10.2.2.2

ISL

Router

10.1.1.2

VLAN 2VlAN 1

Switch Router172.16.1.1

S0 172.16.1.2

To Set Up a WAN Connection

• Encapsulate a dat link searial WAN protocol on the WAN interface

• Assign a network layer address to each interface or subinterface

interface Serial0

ip address 172.16.1.1 255.255.255.0

TCP/IP Command SummaryCommand Description

ip address Sets a switch or router interface IP host address

ip default-gateway Defines a default gateway at the 1900 switch

term ip netmask-format

Changes the subnet mask output for a session

ip netmask-format Changes the subnet mask output for a line

ip host Allows static association of a IP host name to an address

ip name-server Sets the DNS server

no ip domain-lookup Prevents the router from doing IP name lookups

encapsulation isl Defines ISL encapsulation on an Ethernet interface