On 27 Feb 2001, at 12:01, [EMAIL PROTECTED] wrote:
> I want to know how the icmp packet return to the source address in the internal
> network after the packet be NAT or PAT, because after nat ,the icmp packet have
> not information about where it come from internal network ,and the reply packet
> have not information with where it want to arrive in internal network . If use
> nat table , how does the NAT distinguish the reply icmp packets to different
> source addresses which send the icmp request packets to the same outside adress.
AFAIK (and this is how my PIX works, not sure about other FW products)
the FW keeps a mapping table (in the PIX it's called xlate) that relates NAT
addresses to internal addresses, or PAT address/port to internal
address/port. So long as the ICMP packet is returned within the time period
that the table mapping is kept for that particular internal address all the
packets for the process (be it ping, tracert, etc) will get back to the internal
host so long as the FW allows it - if the packet comes back too late the
mapping for the host will be gone and the packet will be discarded.
Dan
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