Cisco 2901 - IP Routing; Specifying a Default Route or Gateway of Last Resort

A-8
Cisco 3900 Series, Cisco 2900 Series, and Cisco 1900 Series Integrated Services Routers Generation 2 Software Configuration Guide
Appendix A Cisco IOS CLI for Initial Configuration
Using the Cisco IOS CLI to Perform Initial Configuration
Examples
Configuring the GigabitEthernet Interface: Example
!
interface GigabitEthernet0/0
description GE int to HR group
ip address 172.16.3.3 255.255.255.0
duplex auto
speed auto
no shutdown
!
Sample Output for the show ip interface brief Command
Router# show ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0 172.16.3.3 YES NVRAM up up
GigabitEthernet0/1 unassigned YES NVRAM administratively down down
Router#
Specifying a Default Route or Gateway of Last Resort
This section describes how to specify a default route with IP routing enabled. For alternative methods of
specifying a default route, see the Configuring a Gateway of Last Resort Using IP Commands tech note.
The Cisco IOS software uses the gateway (router) of last resort if it does not have a better route for a
packet and if the destination is not a connected network. This section describes how to select a network
as a default route (a candidate route for computing the gateway of last resort). The way in which routing
protocols propagate the default route information varies for each protocol.
For comprehensive configuration information about IP routing and IP routing protocols, see Cisco IOS
IP Configuration Guide. In particular, see the “Configuring IP Addressing” chapter and all “Part 2: IP
Routing Protocols” chapters.
IP Routing
You can configure integrated routing and bridging (IRB) so the router can route and bridge
simultaneously. The router will act as an IP host on the network whether routing is enabled or not. To
read more about IRB see the following URL at Cisco.com:
http://www.cisco.com/en/US/tech/tk389/tk815/tk855/tsd_technology_support_sub-protocol_home.html
IP routing is automatically enabled in the Cisco IOS software. When IP routing is configured, the system
will use a configured or learned route to forward packets, including a configured default route.
Note This task section does not apply when IP routing is disabled. To specify a default route when IP routing
is disabled, see the Configuring a Gateway of Last Resort Using IP Commands tech note at Cisco.com.