Re: [lvs-users] Apparent MTU problem using LVS-DR and Windows 2003 RealS

To: users mailing list. <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] Apparent MTU problem using LVS-DR and Windows 2003 RealServers
From: Christopher Smith <csmith@xxxxxxxxxxxxxxxx>
Date: Fri, 18 Sep 2009 03:54:13 -0700
> Just a momentary thought: if this is only occurring with "push"
> transfers to realservers, then there may be some object in the L3 or L2
> path which isn't capable of larger MTU and is disrupting the traffic
> flow.
> Are you, by any chance, using systems connected to a gigabit ethernet
> network? This sounds to me like a possible issue with jumbo frames not
> making it through something - or something like that.

The thing is the problem only manifests when the traffic stays wholly within 
the vSwitch.  As soon as it has to touch some outside device, everything is 

> Alternatively, have you switched off TCP checksum offloading? This has
> been the cause of some problems in the past.

Haven't looked at that, but surely if it can be made to work fine just by 
separating the hosts with another switch, that's not the problem ?

Christopher Smith

UNIX Team Leader
Nighthawk Radiology Services
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