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Community Member

NAT in both directions

If I have 2 routers A and B. Behind router A PC1 is NAT'd to 1.1.1.1 when transmitting to router B. On router B the same PC gets NAT'd to 2.2.2.2 towards router A.

When PC1 transmits to a PC behind Router B does the return traffic have 1.1.1.1 in the headers or 2.2.2.2.

I don't believe it does 2.2.2.2. To verify I would like to be able to capture the traffic coming into the router without a sniffer. I used to have a set of commands that would enable the router to capture traffic coming into the router and the interface it would go out. Similiar to the capture command on a PIX. Is anyone familiar with this command. For some reason netflow comes to mind.

2 REPLIES
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Re: NAT in both directions

In this case we have static NAT on both routers so the router A sends request to 2.2.2.2 with source address 1.1.1.1 and router B sends response to 1.1.1.1 from PC behind router B with source address 2.2.2.2

Community Member

Re: NAT in both directions

Thanks for the reply. I was able to view the traffic using debug IP with an ACL.

Your description of my senrio was correct.

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