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Re: mtu mis-match

  • From: Greg VILLAIN
  • Date: Thu Mar 20 05:40:29 2008

On Mar 19, 2008, at 8:05 PM, ann kok wrote:


I have this problem about mtu mismatch

Some DSL clients, some are working fine.
( ...)

Some DSL clients have this problem
they can't browse the sites.
they can ssh the host but couldn't run the command in
the shell prompt
ping packet are working fine (no packet lost)

but I still don't know why mtu can cause this problem

Thank you for your help

Sounds like the old PPPoE issue : 1500 vs 1492. It usually is dealt with on a per destination basis:

For a given destination (the ones that are causing problems to you) start with :
ping -D -s 1500 <your_destination> and lower the -s value until the ping goes through.
-D forces "don't fragment bit"
-s manages packetsize

When your ping reaches your destination, your -s size is good (for that destination only...).

Independent Network & Telco Architecture Consultant

Greg VILLAIN Independant Network & Telco Architecture Consultant +33 6 87 48 66 14