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Have a got an MTU problem? Advice needed

 
 
thejayman
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      07-30-2005
Hi Group,

We seem to having issues over a Site-To-Site VPN (PIX to CP-NG), this
really shows itself when users are trying to access remote MS Exchange
Email, or large downloads.
Thinking to myself that I they could have an MTU issue I got myself on
one of their server / workstations and started to use the command PING
-f -l ???? xxx.xxx.xxx.xxx.

If I use a value above 1415 I get,
"Packet needs to be fragmented but DF set.". Which to me says I need to
set the MTU on the PIX below this level.

If I go below this value I then get, "Request timed out.". A normal
ping gets a response from the remote host.
The MTU on the inside and outside interfaces of the PIX are set to the
normal value of 1500. Am I looking at this the wrong way? Should I set
the MTU's on both interfaces to 1410?

Thanks in advance for your pearls of wisdom.
Jay

 
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Walter Roberson
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      07-30-2005
In article <(E-Mail Removed) .com>,
thejayman <(E-Mail Removed)> wrote:
:We seem to having issues over a Site-To-Site VPN (PIX to CP-NG), this
:really shows itself when users are trying to access remote MS Exchange
:Email, or large downloads.
:Thinking to myself that I they could have an MTU issue I got myself on
ne of their server / workstations and started to use the command PING
:-f -l ???? xxx.xxx.xxx.xxx.

:If I use a value above 1415 I get,
:"Packet needs to be fragmented but DF set.". Which to me says I need to
:set the MTU on the PIX below this level.

Check out the sysopt for tcpmss .
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"You're all freaks, sir. But you always have been freaks.
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