Not able to manage ESX from vSphere Client/vCenter --> How to associate Service Console to VMNIC0 (Phy NIC0) from CLI

ESX Server 3.x Service Console NIC Assignment (VMware KB 8018438)
--> During Installation of ESX did not assign Service Console to Phy NIC
--> or Can't Associate Network Card with Service Console
--> or Due to some problem (or messed up), Service Console is currently not assigned to Phy NiC

Details
When installing ESX Server 3.x, you are not given the option to select which network card should be associated with the service console. By default, it seems as though vmnic0 is selected.

Solution
Note: This article assumes that the correct network settings (IP Address, Subnet Mask, Gateway and DNS) were assigned during the initial installation.

To resolve this issue, use the esxcfg-vswitch command, as follows:
To the physical switch, attach only the network cable used for the service console.

List all of the network adapters from the ESX Server service console and locate the name of the vmnic# that has a link status of up.
# esxcfg-nics –l
If vmnic0 has a link status of up, stop now. Otherwise, remove vmnic0 from vSwitch0.
# esxcfg-vswitch -U vmnic0 vSwitch0

Associate the vmnic# that has a link status of up from step 2.
# esxcfg-vswitch -L vmnic# vSwitch0

Use the following commands to determine where the ESX Server service console portgroup is (if you are doing a repair after changing physical NICs or similar activity, for example):
# esxcfg-nics -l
Determines which NICs are link up esxcfg-vswif -l to ensure Service Console is the port group, and the settings are correct.

# esxcfg-vswitch -l
Shows which vSwitch the service console port group is in.

# esxcfg-vswitch -L
Links the vmnic and service console together.

Prior to changing the IP address of Service Console on ESX hosts

Take the following into consideration prior to changing the IP address of the Service Console:

• Changing the primary Service Console's IP address may result in network connectivity loss.
• Connect to ESX shell via a remote console or a KVM console. The PUTTY or SSH connection terminates during IP address change.
• VMware HA and DRS, if enabled, must be disabled to eliminate failover.
• Disconnect and remove the host from VirtualCenter.
• Change the DNS database for the forward entries and the reverse entries if applicable.
• For manual resolution in /etc/hosts, change the IP for each ESX host in the VMware HA cluster and, if needed, in any other host in your environment.
• If there is more than one Service Console present, determine the primary one by checking /etc/sysconfig/network for default gateway device and IP address.

Changing the IP address on ESX 3.x and 4.0

To change the IP address on ESX 3.x and 4.0: 

1. Log in as root to the ESX host console using a SSH or KVM connection.
2. Run the following command to stop the network service:
   service network stop
    
3. Run the esxcfg-vswif command to change the IP of the hosts:
   esxcfg-vswif -i NEW_IP_ADDRESS -n MASK_ADDRESS vswif0
    
4. Edit the /etc/sysconfig/network file and change the gateway IP if needed.
5. Run the following command to restart the network:
   service network start
    
6. Add the host back to VirtualCenter using a FQDN (preferably) or by its IP.
7. Reconnect host to VirtualCenter (if applicable).   

Changing the IP address on ESX 2.5

To change the IP address on ESX 2.5:

1. Log in as root to the ESX host console using a SSH or KVM connection.
2. Run the following command to stop the network service:
   service network stop 
   
3. Change the IP and net mask in the correct file. Edit the /etc/sysconfig/network-scripts/ifcfg-eth0 file and change the IP and the net mask.
4. Change the gateway configuration. Edit the /etc/sysconfig/network file and change the gateway IP if needed.
5. Run the following commands to restart the interface and the network:
   
   • ifdown eth0
   • ifup eth0
   • service network start