NAT on multiple routers

[iores]

Hi,

Is it possible to configure NAT on multiple routers? I need to perform outside NAT, and NAT sessions should be in sync between routers somehow in case packet enters via one, and exits via other router.

Are there any other options?

[M02@rt37]

Hello @iores 

From my point of view, best option is to ensure symmetric routing so that traffic always traverses the same router for a given session.

If failover is a concern, consider an external stateful firewall/load balancer...

[paul driver]

Hello
Yes it is applicable to have nat resiliency and but can you elaborate on your topology please

[iores]

Hi,

I have 3 routers - A, B, and C. Each router has one physical link with one DC router; totally three separate links, primary, secondary, and tertiary. Behind DC routers is 192.168.1.0/24 network. 

So I have to perform outside NAT, and translate 192.168.1.0/24 to some other segment. NAT has to be on all three routers - A, B, and C.

Routers are cisco 4K.

Is there a way to do it?

[Richard Burts]

You have told us about the 3 routers connecting inside to one DC router and through it to 192.168.1.0/24. Can you tell us about the 3 routers outside connections? Are they all connected to the same ISP or to different ISPs?

I believe that there are several issues, and the most significant issue is that when the original packet was forwarded to ISP the router that performed the translation created an entry in a table with information about that packet (which would be used when the response was received). If there was some issue and the response packet comes to a different router, how does that router know what would have been in the translation table of the original forwarding router?

[Joseph W. Doherty]

Cisco, in the past had stateful NAT (SNAT), but a quick skim appears Cisco no longer provides it.

[paul driver]

Hello Joseph
their is now box to box nat (B2B)