North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical


  • From: Steven M. Bellovin
  • Date: Thu Sep 13 20:26:59 2001

In message <[email protected].co
m>, Vandy Hamidi writes:
>I know that in Tunnel Mode, IPsec can be NATed and PATed (without IKE on UDP
>500 being used), but as I'm trying to break down the process of  how it is
>working, I've been stumped by this:
>NAT - Changes source IP during translation
>PAT - Changes source IP and TCP/UDP port to another to track multiple to one
>My question is, how does PAT track the packets with their internal hosts
>when there is not a TCP/UDP header to translate.
>How does it know which "internal" host a returning ESP packet must be
>forwarded to after it un PATs the incoming packet?
>thanks and I hope this isn't a totally stupid question.  If it is, humor me

IPsec can't be PATted, because the TCP and UDP port numbers are in the 
protected part of the packet.

		--Steve Bellovin,