Ping Packet size problem

[us3r]

I have a few linux servers that have problems pinging over a serial connection (between 2 cisco routers) if the packet size is larger than 1742.
The connection works fine for Windowz PC's.
Any ideas as to what the problem with linux might be?

 

[pansophic]

What is your MTU size? It could be that you are simply exceeding your MTU, although 1741 would be a unique size.
pansophic

 

[us3r]

how do I double check that and change it to do testing?

 

[pansophic]

ifconfig does it in linux, I think that ipconfig in Win2k will do it.

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:10 errors:0 dropped:0 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:932 (932.0 b) TX bytes:932 (932.0 b)

pansophic

 

[us3r]

eth0 Link encap:Ethernet HWaddr 00:02:55:7B:32:AA
inet addr:192.168.100.60 Bcast:192.168.100.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

Here I can see the MTU is 1500. How do i change this (if I should) and what effects will it have on a system?

 

[pansophic]

You can change the MTU size, but it is not recommended, because it defines the maximum size of a packet on your local network. 1500 is a very common size.

Are your windows machines reporting the same MTU size?

Is there a reason that you wish to ping with such a large packet?

Can you ping with any packet size in excess of 1500 on your linux box(es)?
pansophic