Changing ESXi IP address and default route via command line

esxcfg-vmknic "Management Network" -i [newip] -n [newsubnetmask]
esxcfg-route -d default 0.0.0.0 [olddefaultgw]
esxcfg-route -a default 0.0.0.0 [newdefaultgw]
/sbin/services.sh restart