BGP and NAT Not working

bgpnat;

I have an odd issue with BGP+NAT. I have 2 separate routers and 2 different ISP's.

Topology looks like this:

ISP1--BGP--> RTR1 \
                     \--OSPF-- Palo Alto Firewall-- Internal Network
ISP2 ---BGP--> RTR2 /

Hope that makes sense.

So I currently have BGP and NAT working with just ISP1 on RTR1. However, when I turn up ISP2, advertise our /24, and issue the NAT commands on RTR2 as well, NAT stops working. Am I missing something here?

Thanks

Best Answer

If I understand correctly you are performing NAT for your traffic going to the Internet on RTR1 and RTR2.

If the NAT tables are not synched between those 2 routers, then if a NAT translation is performed on RTR1 for example, but the answer come through ISP2 to RTR2, then RTR2 doesn't have a NAT entry for this traffic and cannot forward it to the originating host.

The solution is either to synch NAT tables between the 2 routers (depends on the routers models) or to perform NAT on another device and only route on the BGP routers.

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