When you installed VMware vCenter Appliance 5.5 from OVA file, often forgot to enable network port.
Here is how to enable and add/change IP address thru console port.
1. Power on the VM / vCenter and choose "open console"
2. You would see below
3. After login, type "./vami_config_net from /opt/vmware/share/vami
4. Choose menu option what You want to change.