Want to check/confirm whether a Cisco/Juniper router "Advertising" a route

Hi Rene,

  1. What would be the command(s) to check/confirm whether a Cisco/Juniper router “Advertising” a “Route”.
  2. If I need to assign a NAT IP on a device in a network, how I will check what is the next available NAT IP in the network?

Can you please help me to understand both with a scenario.

Thanks & Regards,

Hello Manami

For these questions, I can answer from the point of view of Cisco.

There is no one command that will show you exactly what routes are being advertised. It depends on the routing protocol you are using. If you are using EIGRP, you can use any of the following. Note some links to the Cisco command reference for more information:

  1. Look at the EIGRP configuration in the running-config and determine which networks are being advertised. Check to see that no passive interfaces are blocking such advertisements as well as distribution lists.
  2. show ip eigrp events - this command will display the EIGRP event log which shows when an advertisement is being sent
  3. show ip eigrp topology ip_address - this command can be used on neighbouring routers for the specific prefix in question. The output will also include the originating router so you know from which router the route has been learned.

For OSPF, it is somewhat easier. You can use the show ip ospf database self-originate command to see all of the LSAs that are being generated by the local device.

Unfortunately there’s no single silver bullet solution, you still have to do a bit of digging, but it’s not too bad once you understand the output of these commands.

If you are talking about static NAT, then you will have to go into the NAT router and determine the current NAT translations using the command show ip nat translations. Once you see which IPs are already in use, you can know the next free available one and configure it accordingly.

I hope this has been helpful…


What should I use for BGP?


Hi Manami,

BGP has a useful command to see the advertised routes:

show ip bgp neighbor advertised-routes