NAT Pool Address in not connected segment

Rakhmadian Purnama · ‎09-04-2013

Hi Guys,

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

I'm going to NAT my server from IP 10.250.1.100 to 192.168.1.X, let say 192.168.1.10. 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..

Regards,

Rp

Karsten Iwen · ‎09-04-2013

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 192.168.1.0/24 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 192.168.1.0 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

Rakhmadian Purnama · ‎09-04-2013

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 255.255.255.0 null0

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

Does it possible a proper solution ?