Because ESXi 5.x has no Service Console, migrating from ESX 4.x to ESXi 5.x removes the Service Console port group.

After the migration to ESXi 5.x, a new port group, the Management Network port group, is created.

If any of your ESX hosts require the Service Console port group to support an existing service, you can write a firstboot script to recreate the port group after the migration. See the information on the %firstboot command in Installation and Upgrade Script Commands.