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Default Rout using: ip default-network

fjcardenas-1
Level 1
Level 1

Hello,

I am a little confused with how to use the ip default-network command to configure a default route. Can someone explain the difference using "ip default-network" and "ip route"?

Thanks.

4 Replies 4

Jerry Ye
Cisco Employee
Cisco Employee

Hi Francisco,

You would use ip default-network when your device is configured with no ip routing. It really means device doesn't need to perform any kind of routing (like a PC) and use the IP address as its default router/gateway.

When you are using ip route, ip routing must be configured. ip route means you want to set up a static route for certain destination.

HTH,

jerry

Correction...

It should be ip default-gateway.

jerry

More correction,

ip default-network is used to select a network as a candidate route for 0.0.0.0/0.

ip route is static route entry that will go into the routing table.

To explain this in an example:

ip route 172.16.0.0 255.255.0.0 172.16.1.1

ip default-network 172.16.0.0

when a packet destinated to 172.16.0.0/16 network, router will route it to 172.16.1.1, at the same time, when a packet destinated to network has no specific match in the routing table (0.0.0.0/0), router will use the 0.0.0.0/0 and send it to 172.16.0.0 network.

Regards,

jerry

Giuseppe Larosa
Hall of Fame
Hall of Fame

Hello Francisco,

some protocols support the ip default-network concept:

instead of simply specifying a default gateway or advertising a default route 0.0.0.0/0, the protocol can send out an advertisement for the IP subnet of the default network with a special flag that says that it can be used as exit point to outside world.

The protocols that support ip default-network are RIP, IGRP and EIGRP.

To be noted that the ip default-network have to reference a different major network (class A,B, C) then the one used internally.

Also EIGRP and IGRP require a network command for the ip subnet for being able to send the IP route with the external flag.

Hope to help

Giuseppe

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