From: Michelle T (mtruman@xxxxxxxxxxxxxxx)
Date: Wed Jan 03 2001 - 15:45:10 GMT-3
This makes a lot of sense. That key-word was breaking my NAT set up and now
I understand why. The host I was coming from was not a part of the NAT pool
I had allocated, so the match host action probably couldn't be performed.
Thanks!
(14 days to go...)
----- Original Message -----
From: "Jay Hennigan" <jay@west.net>
To: "Michelle T" <mtruman@mn.mediaone.net>
Cc: <ccielab@groupstudy.com>
Sent: Wednesday, January 03, 2001 12:32 PM
Subject: Re: IP Nat and the "Match-Host" keyword
> On Wed, 3 Jan 2001, Michelle T wrote:
>
> > Can someone help me make sense of the "match-host" keyword in IP NAT?
> > Cisco's definition is listed below, and I still just don't get it.
> >
> > Host Number Preservation:
> > For ease of network management, some sites wish to translate prefixes,
not
> > addresses. That is, they wish the translated address to have the same
host
> > number as the untranslated address. Of course, the two prefixes must be
of
> > the same length. This feature can be enabled by configuring dynamic
> > translation as usual, but configuring the address pool to be of type
> > "match-host":
> > ip nat pool fred <start> <end> prefix-length <len> type match-host
>
> Think of the fundamentals of IP subnetting, where an address is divided
> into a network part and a host part. This option, with the requirement
> of equal prefix length, maps the host part one-to-one.
>
> What this keyword does is keep the host bits the same across both sides of
> the NAT. So, for example, if the inside is 192.168.1.x/24 and the outside
> is 172.16.200.x/24, then 192.168.1.123 would map to 172.16.200.123, etc.
> ^^^ ^^^
> This holds true regardless of the subnet mask. A less intuitive example
> would be 192.168.1.64/26 mapping to 172.16.5.0/26. Here, the inside host
> of 192.168.1.77 (host bits 001101) would map to 172.16.5.13 (also 001101).
>
> --
> Jay Hennigan - Network Administration - jay@west.net
> NetLojix Communications, Inc. NASDAQ: NETX - http://www.netlojix.com/
> WestNet: Connecting you to the planet. 805 884-6323
>
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