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I am using CentOS 5 in my environment and it acts as a gateway for my LAN. My eth0 interface MTU is set to 1500 (default).

UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

Recently I am facing a strange problem where some of the websites simply hangs. If I change the MTU to 1492 the same websites open in the browser but then SSH connections hangs at that time.

What could be the problem and how do I fix it ?

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Are you changing mtu on the router, switch (if any) and server, or do you only change the server's mtu? –  Mike Pennington Oct 9 '12 at 11:00
    
@MikePennington I am changing the MTU in the server (CentOS 5) which acts as a router for a LAN. From the server I am trying to browse the websites or make a SSH connection to servers outside our network. –  Supratik Oct 9 '12 at 11:09
    
Check your firewall and make sure you aren't blocking ICMP type 3. –  Michael Hampton Oct 9 '12 at 13:30

1 Answer 1

All interfaces in the subnet need to have the same mtu... set them all to 1492, including your ethernet switches (if possible)

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