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The default route as configured in a Cisco router is as shown below:

Gateway of last resort is 103.0.0.0 to network 0.0.0.0

What I have came across so far is that the gateway of last resort is configured to a specific IP address such as 172.16.2.1. In this case where it is a network address, does the router choose the most specific route with lowest metric as the default route IP address? Does this also mean that the default route may change depending on the destination IP address?

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    Could it be 103.0.0.0/7? In that case it's just a host address.
    – manish ma
    Apr 13, 2021 at 2:38
  • Could it be an indirectly connected loopback /32? Which will require recursive lookup to determine the actual next hop address?
    – manish ma
    Apr 13, 2021 at 2:54
  • Could it be a virtual IP address of VRRP?
    – manish ma
    Apr 13, 2021 at 2:59
  • 2
    Cool, you can also check FIB to make sure. I think in Cisco it's: show ip cef
    – manish ma
    Apr 13, 2021 at 3:42
  • 1
    Thanks a lot, it does show up there. It seems like FIB is sometimes more informative than routing table.
    – iridescent
    Apr 13, 2021 at 3:44

1 Answer 1

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In an EIGRP network, how do you advertise a default route to all the routers?

There are a few ways to advertise a default route to the rest of the network.

  1. Create a static route on the border router (of the EIGRP domain) and redistribute it into EIGRP.
  2. Create a summary route (0.0.0.0) on the border router.
  3. Use the default-network command on the border router to generate a default route.

The 2nd and 3rd techniques will give you the output you've shown.

default-network is a hold over from classful routing and is rarely used anymore.

Cisco has some good explanations here and here.

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