Default Routing

Good Day,

Been doing alot of reading to find the difference between static default routing using the ip route command and default routing using the ip default-network command.

could someone please provide a clear explanation of the difference please.

Thank you.

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Comments

Xenz

Been a while since I worked with ip default-network, so maybe someone will correct me if I'm wrong. So if I remember right...

when configured, ip default-network is automatically sent via routing protocols while ip route is not.

billscott92787

I definitely know that the ip route command can be used to configure a default route which is not automatically sent via routing protocols. You would have to configure it to send these updates. Like if you were using RIPv2.

Router#configure terminal
Router(config)#router rip
Router(config-router)#redistribute static

It appears that the ip default-network command is used when "ip routing" is enabled. You can see a good explanation at ciscos website: Configuring a Gateway of Last Resort Using IP Commands - Cisco Systems

It appears that if you use this command, and the router has a "route" to the network, it will be flagged as the "Candidate" or preferred route, I am assuming see my example from packet tracer:

Before ip-default network 10.0.0.0 command: (routing table)

Gateway of last resort is not set

C 10.0.0.0/8 is directly connected, Loopback0
C 192.168.1.0/24 is directly connected, Serial0/0
C 192.168.2.0/24 is directly connected, Serial0/1

After using the ip-default network 10.0.0.0 command (routing table)

C* 10.0.0.0/8 is directly connected, Loopback0
C 192.168.1.0/24 is directly connected, Serial0/0
C 192.168.2.0/24 is directly connected, Serial0/1

As you can see it flagged that route. In addition, it is true that it appears to send this update automatically via routing protocols updates. See my Second routers routing table:

C 192.168.1.0/24 is directly connected, Serial0/0
R 192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:06, Serial0/0
R* 0.0.0.0/0 [120/1] via 192.168.1.1, 00:00:06, Serial0/0
Router#ping 10.10.10.1 (This is a Loopback0 interface on my first router)

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 31/31/32 ms

As you can see, I didn't configure the route, it was automatically sent via RIP.

Forsaken_GA

Whether or not your default route is propagated into a routing protocol depends on the protocol itself. Some make use of ip default-network, some make use of default-information originate. Knowing which protocols require which would be a very good idea.

Then there's route redistribution...