'ip default-network' command

Nov 27, 2005 2 Replies
Y

I have few questions regarding the confusing 'ip default-network' command. I would appreciate your help on this.


  1. I understood that this command does not benefit the router it is configured on, but only the rest of the routers. Is that true?
  2. EIGRP router with this command redistributes the actual network to the rest of the routes, but not the actual 0.0.0.0 default route. Does it mean that the rest of the routers will use this network route only, or treat this next hop as the gateway for all traffic?
  3. How does the routers actually passes the '*' indicator between them?

Thanks in advance.


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H

Not true.

Here's how the default-network command works. Say you have in your routing table the following:

172.16.1.0 /24 next hop 172.16.1.5 10.0.0.0 /8 next hop 10.1.1.1 192.168.1.0 /24 next hop 192.168.1.5

Now you type "ip default-network 172.16.0.0"

*BECAUSE* you have a route in the 172.16.0.0 /16 address space, it will use the next hop address to 172.12.1.0 /24 (172.16.1.5 in my example) as the candidate default route.

The "passing" of '*' (i.e. default routes) is IGP dependent. OSPF will react differently from EIGRP from RIP for example.

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