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NAT Pool Address in not connected segment

Hi Guys,

I have a little bit question about NAT Addressing, here is the topology :

NAT Diff NET.jpg

I'm going to NAT my server from IP to 192.168.1.X, let say I know that IP NAT pool address should be advertised in the routing. When we use static routing it can be completed without issue. But the question is : How to advertise it into dynamic routing such as OSPF, RIP, EIGRP, etc. ? Ex. I want to run OSPF between RTR-A and RTR-B.

As far as I know, you can advertise it when your network segment is attached on interface (connected network). But in this case, the segment 192.168.1.X /24 is not attached on any interface in the router. I have tried advertise it using network command in the OSPF at RTR-A, but when I type show ip route ospf in RTR-B, the segment 192.168.1.x doesn't appear.

I'm sorry if this is reposting, because I don't know the best keyword the find it in Google..



Everyone's tags (3)
VIP Mentor

Re: NAT Pool Address in not connected segment

Let's assume that Router-A is the customer and Router-B belongs to the ISP and you are a small customer that doesn't run BGP with the ISP. In this scenario the ISP is responsible for the routing of the network. And of course we assume that there are more routers behind RTR-B.

On router-B it can be done in different ways.

1) very common is to have a secondary Network configured on the link between A and B. Better would be to have a static route on Router-B for network pointing to router-A. In both cases, router-B can redistribute the IP-network and make it reachable. This is not the responsibility of router-A.

Sent from Cisco Technical Support iPad App

NAT Pool Address in not connected segment

Hi karsten,

Nice explanation, I agree with you..

But, I have found a case in my customer where the customer's router actively advertise the NAT address to provider.

In customer's router configuration I've found :

ip route 192.168.1.x null0

and then, they advertise it into dynamic routing protocol using network command.

Does it possible a proper solution ?

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