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Asked: 2011-01-15 10:20:56 +0800 CST

Is it possible to ping through a NAT?

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It it possible for a PC behind a NAT ping to a device that is on the outside of the NAT and get a successful response? (assuming the firewall permits it)

This is a Cisco RV 120W router

networking cisco nat ping

4 Answers

  1. Best Answer

    I don't see why not as long as the router/firewall allows outbound ICMP and the inbound responses.

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  2. It is quite possible, the router just has to allow it. I don't know that specific router though.

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  3. Yes. As long as the router allows the Ping request to pass outbound and properly tracks the request so that it can return. Most routers I have dealt with handle this correctly. Pings in though a Firewall (NAT or not) are often blocked.

    There are tools which manipulate TCP packets to generate ICMP failures to provide the equivalent functionality through a Firewall.

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  4. The ICMP protocol has to be allowed though the routing devices.

    If you have some doubt, you can run the traceroute (Linux) or tracert (Windows) command, to see up to which device the ICMP protocol is allowed.

      tracer[ou]t[e] IPaddressOrDomain

    While you see 

      IP/Domain  time1 time2 time3

    the protocol goes through.
    But when you see a series of (or infinite)

      * * *

    the protocol is dropped/blocked or a device on the way back prevents the protocol to be routed.

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