Advertising default routes of OSPF to other devices

[elker_7777777]

My prof told us to "Enable and configure OSPF routing on the two switches and two routers"

Basically I have 2 Routers, and each of them are hooked up to an ISP router, and internally they are each hooked up to 2 switches (so a total of 3 connections each) and I have done the "no switchport" command (as well as assigning ip addresses) on the 2 interfaces of each switch so this whole area is layer 3

My prof has asked that I:

1) configure a default route on the 2 routers

so I did

#ip route [ISP interface address]

on each router (different ip in each case)

2) "advertise the default routes to the other layer three devices in the LAN"

Here I am stuck. I have looked everywhere online and I cannot find how to do this. I read a bit about some "default-information" command and tried them all but the commands didn't even register

Please help,

Az

[Reza Sharifi]

If you already have a default route pointing to the IP address of the ISP "ip route 0.0.0.0 0.0.0.0 <isp ip address>" on both routers, than you need to insert the default route into OSPF, so your other devices can have access to outside.

config t

ip router ospf xx

default-information originate

HTH

[SOHAN HEGDE]

hi,

You can use below command to advertise default route to switches.

router ospf "Process-id"
 default-information originate

[Jon Marshall · Accepted solution]

A quick query found this link which covers how to inject a default route into different OSPF area types -

http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13692-21.html

basically having a default route is not enough with OSPF, you need to use the "default-information originate ...." command and the details are in the above link.

Jon

[elker_7777777]

Thank you, I realized my mistake was that I didn't understand the command default-information originate, and was using it on the target routers, not the ones holding the default routes, but reading the link, I realized when it said that said command makes the routers ASBR, that I should be using it on my original ones, and not the switches.

[Jon Marshall]

No problem, glad you got it working.

Jon