I've got a couple of vSphere 5.0 hosts in a small lab environment here and I've noticed a strange behaviour. When on of the hosts gets rebooted, it is unresponsive to the network until I log into the ESX console, Press F2 to customize and select Restart management network. Once this is done, the networking works perfectly as expected.

Each host has two NICs which are trunked together using Etherchannel to a Cisco 3750. The link is also a .1q VLAN trunk and the management network is configured on VLAN121 with the VM traffic configured on VLAN118.

Why would the host be completely dead to the world until I physically kick it?

Edit

Sample switch config for trunk:

interface Port-channel2
 description Blade 1 EtherChannel Trunk
 switchport trunk encapsulation dot1q
 switchport mode trunk
end
!
!
interface GigabitEthernet4/0/1
 description Bladecenter1 CPM 1A
 switchport trunk encapsulation dot1q
 switchport mode trunk
 speed 1000
 duplex full
 channel-group 2 mode on
end

Vswitch teaming settings:

Management port group settings: