Published on 2024-09-12 01:13 by Niladri Das

Introduction to Default Routing

Default routing is a technique used to forward packets to a default gateway when the destination network is not present in the routing table. It is used to provide a fallback route when no other route is available.

Theory

Default routing uses the following key concepts:

• Default gateway: The default gateway is the router that packets are sent to when the destination network is not present in the routing table.
• Static routes: Static routes are used to configure default routing in routers.

Summary

Default routing is a simple technique used to provide a fallback route when no other route is available. It is commonly used in networks where there is a single exit point to the internet.

Configuration and Verification

R1 (Default Route)

R1 Configuration

Router>enable
Router#configure terminal
Router(config)#hostname R1
R1(config)#interface fa0/0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface serial0/0/0
R1(config-if)#ip address 192.168.12.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#clock rate 64000
R1(config-if)#exit
R1(config)#ip route 0.0.0.0 0.0.0.0 192.168.12.2
R1(config)#exit

R1 Verification

R1#show running-config
R1#show ip route
R1#write

R2 (Static Route)

R2 Configuration

Router>enable
Router#configure terminal
Router(config)#hostname R2
R2(config)#interface fa0/0
R2(config-if)#ip address 192.168.2.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial0/0/0
R2(config-if)#ip address 192.168.12.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial 0/0/1
R2(config-if)#ip address 192.168.23.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#clock rate 64000
R2(config-if)#exit
R2(config)#ip route 192.168.1.0 255.255.255.0 192.168.12.1
R2(config)#ip route 192.168.3.0 255.255.255.0 192.168.23.2

R2 Verification

R2#show running-config
R2#show ip route
R2#write

R3 (Default Route)

R3 Configuration

Router>enable
Router#configure terminal
Router(config)#hostname R3
R3(config)#interface fa0/0
R3(config-if)#ip address 192.168.3.1 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface serial0/0/0
R3(config-if)#ip address 192.168.23.2 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#ip route 0.0.0.0 0.0.0.0 192.168.23.1

R3 Verification

R3#show running-config
R3#show ip route
R3#write

Written by Niladri Das