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New Member

NAT with multiple outside interfaces

Is this possible?

routerA connects to routerB witch connects to routerC and back to routerA.

RouterA connects to the WAN or (internet)

Each router has three interfaces.

The loop is for redundancy in case of a circuit outage.

All routers run OSPF.

routerB performs NAT for networkB

routerC performs NAT for networkC

Question is:

Is it possible to define (ip nat outside) on both of the (WAN) interface connections on routerB and routerC?

Goal is to have the NAT service work regardless of what external interface is being used.


New Member

Re: NAT with multiple outside interfaces

A diagram would be helpful in this scenario mate. Can you provide one?


New Member

Re: NAT with multiple outside interfaces

Yes, I believe it should be possible.

Configure the link from RouterA to RouterB and RouterC to "ip nat inside" and specify the outside NAT address of routerB and routerC.

Configure the link to the WAN interface (internet) with "ip nat outside" and be sure to create a global outside IP for NAT or use the WAN interface itself to use PAT.

It's the infamous double-NAT, messy but it should work. Difficult to troubleshoot if you have MTU or TCP windowing problems, or any type of problem later.

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