ESX/ESXi's vSwitches are just that, switches, nothing more or less, and can happily handle both jumbo and regular frames. By default ESX/ESXi itself won't use jumbo frames (for v4.0-v.4u1 anyway) without the instructions below. So I suspect that your Centos guest itself is trying to use jumbo frames, obviously you can switch them off if you're infrastructure can't/doesn't handle them well but overall I wouldn't worry about it.
To switch on ESX/ESXi jumbo frame support do the following either from an SSH session or via the VMa;
esxcfg-vswitch -l (which lists the current vSwitch MTU)
esxcfg-vswitch -m 9000 vSwitch0 (which sets the MTU at 9000)
esxcfg-vswitch -l again to check it's set, repeat for other vSwitches if you like.
If you have a cluster I'd be tempted to do these changes with the host in maintenance mode then immediately reboot and check MTU again before putting the host back into the cluster.