MTU != 1500 in KVM guest

Hi list,

I urgently need to set a MTU >1500 in KVM guests. However, using the 'usual procedures' (on CentOS) do not happen to work.

I'm running CentOS 5.5 x86_64 on the mare metal as well as the KVM guest; KVM is

kmod-kvm-83-164.el5_5.25
kvm-83-164.el5_5.25

Is there anything I didn't see yet?

Thanks,

Timo