really surprised for the fact that you are trying to configure GW for vmotion....as mentioned by many others.. there is no need of GW for vmotion...
just install esxi... give static ip, GW, dns for the management console..
then just create a vswitch for the vmotion and add nics..then set vlan and give ip thatss..it ..even though vmotion show the GW of magagement vmkernel... the vmotion dont use that GW...by default it will be greyed out... and when you tries to give a GW then the GW of the management also changes...
so just give ip to the vmotion network..
AGAIN there is no need to give any GW for vmotion port group...