ip default-network

[fjcardenas-1]

I understand how default routes with "ip route" command work but I am confused with how default routes work with the "ip default-network" commando.

Do you configure a default route using this "ip default-network" command only when you learn a network with a routing protocol? or can you use this command even if there is no a routing protocol?

Thanks.

[Tshi M]

Either you learn it through routing protocol or you have a static route to that network. See below:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml

[Peter010101]

To select a network as a candidate route for computing the gateway of last resort, use the ip default-network command in global configuration mode.

Usage Guidelines

The Cisco IOS software uses both administrative distance and metric information to determine the default route. Multiple ip default-network commands can be given. All candidate default routes, both static (that is, flagged by the ip default-network command) and dynamic, appear in the routing table preceded by an asterisk.

If the IP routing table indicates that the specified network number is subnetted and a nonzero subnet number is specified, then the system will automatically configure a static summary route. This static summary route is configured instead of a default network. The effect of the static summary route is to cause traffic destined for subnets that are not explicitly listed in the IP routing table to be routed using the specified subnet.

Examples

The following example defines a static route to network 10.0.0.0 as the static default route:

ip route 10.0.0.0 255.0.0.0 10.108.3.4

ip default-network 10.0.0.0

If the following command was issued on a router not connected to network 10.140.0.0, the software might choose the path to that network as a default route when the network appeared in the routing table:

ip default-network 10.140.0.0