VMware ESXi management IP/vSphere connectivity might become suddenly unavailable over the time or after replacing the network interface card.
This can be easily resolved by removing the vmnic port groupe for the management network and add it back again to the vSwitch. You will need direct console access to the ESX shell to perform these actions.
1. Press CTRL+F1 to access the ESXi CLI shell and enter your root password.
2. Remove the vmnic management network port group :
esxcfg-vmknic -d "Management Network"
3. Add back the vmnic with your management IP information :
esxcfg-vmknic -a -i <IP_Address> -n <NETMASK> "Management Network"
esxcfg-vmknic -a -i 192.168.1.100 -n 255.255.255.0 "Management Network"