[lvs-users] director and real servers on different subnets

Kelsey Cummings kgc at corp.sonic.net
Wed Sep 19 17:32:07 BST 2012

On Wed, Sep 19, 2012 at 03:08:55PM +0200, Marcin Niskiew wrote:
> I also read about IP Tunneling - but it's not mentioned on Centos docs
> (it's not supported?)

IP Tunneling is supported and works fine under most circumstances.
Today, it requires that clients have functional PMTUD (99.999% of clients
will?) or MSS fixup on the real servers.  There's a patch that Julian
worked on that allows for the lvs box to frag the tunneled packets but
I'm not sure what the state of that is.

It is covered pretty clearly on



See this for PMTUD and MSS Fixup, although you are probably better off
running the MSS fixup on each of the real servers.  (Just limit it to
the load balanced traffic, ie, source ip of the virtual server


Kelsey Cummings - kgc at corp.sonic.net      sonic.net, inc.
System Architect                          2260 Apollo Way
707.522.1000                              Santa Rosa, CA 95407

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