MTU - After some information

[ahuxham]

Hi Folks,

 

Just a quick query regarding MTU size. Our new site is due to go live in a few weeks, and we've setup a S2S VPN Connection. The new site is due to have Sun Ray terminals connecting back to the main site into a Sun Ray Server and ESX Server.

 

We've tested the Sun Rays at home, now obviously our internet connections at home aren't that great, so we've been following advise on setting MTU limits to what the WAN link can handle.

 

Currently 1391 is a safe MTU and no fragmentation on the packet, obviously the new site will have a similar MTU.

 

If we set both VPN Routers at a MTU transmit max of say 1300, what happens to our current infrastructure that still runs at 1500 MTU. All our local machines, servers all have a default of 1500.

 

Anyone have suggestions or ideas or a decent explaination?

 

Thanks.

[xenonive]

the communction server to server within same network will remain 1500 , but server over vpn will be fragmented to the MTU limit you place on router(VPN). This will cause slow down if servers are talking over VPN , best to change the MTU on the other machines in the network , this can be done via reg

 

HKEY_LOCAL_MACHINE\SYSTEM\CurentControlSet\Services\NdisWan\Parameters\Protocols\0

 

change the ProtocolMTU value.

 

http://support.microsoft.com/kb/826159 might also be of help

Edited December 7, 2009 by xenonive