Default Routing

Default Route is also known as gateway of last resort which is a special type of static route. Static route allows traffic to be forwarded even without a specific route to a particular network.In default route all network and subnet mask is identified by all zeros (0.0.0.0 0.0.0.0).

• It is used when the destination is unknown, for example internet.
• It can also be used at the end location where there is only one exit path for any destination.
• Default routes help in reducing the size of your routing table.
• If the routers do not find an entry for the destination network in a routing table the router will forward the packet to its default route.
• It’s also known as default gateway.

Router 0:
Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface FastEthernet0/1
Router(config-if)#ip address 192.168.10.1 255.255.255.0
Router(config-if)#no shutdown
%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
Router(config-if)#exit
Router(config)#interface Serial 0/1/0
Router(config-if)#ip address 192.168.30.1 255.255.255.0
Router(config-if)#clock rate 64000
Router(config-if)#no shutdown
%LINK-5-CHANGED: Interface Serial0/1/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1/0, changed state to up
Router(config-if)#exit
Router(config)#do write
Building configuration...
[OK]

• Configure a Default Routing Protocol:
Router(config)#ip route [destination network] [subnet mask] [next hop/exit interface]
Router(config)#ip route 0.0.0.00.0.0.0 192.168.30.2

Router 1:
Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface FastEthernet0/0
Router(config-if)#ip address 192.168.20.1 255.255.255.0
Router(config-if)#no shutdown
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
Router(config-if)#exit
Router(config)#interface Serial 0/1/0
Router(config-if)#ip address 192.168.30.2 255.255.255.0
Router(config-if)#no clock rate
This command applies only to DCE interfaces
Router(config-if)#no shutdown
%LINK-5-CHANGED: Interface Serial0/1/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1/0, changed state to up
Router(config-if)#exit
Router(config)#do write
Building configuration...
[OK]

• Configure a Default Routing Protocol:
Router(config)#ip route [destination network] [subnet mask] [next hop/exit interface]
Router(config)#ip route 0.0.0.0 0.0.0.0 192.168.30.1