This KB addresses issues that arise when a "block all ingress traffic" rule is mistakenly added during the creation or edition of vCenter firewall rule.
Symptoms:
Attempts to make firewall changes from vCenter VAMI result in losing access to vCenter
This could happen if an incorrect IP is entered, an entire subnet range is blocked, or the iptables service is mistakenly enabled from the command line
vCenter services will be up and running but vCenter UI will not be accessible.
iptables -nL | less
This will give the list of firewall rules
chkconfig iptables off
iptables-save > /var/tmp/iptables.rules.default
cp /var/tmp/iptables.rules.default /root/var/tmp/iptables.rules.default.backup
vi /var/tmp/iptables.rules.default
iptables-restore < /var/tmp/ iptables.rules.default
iptables -nL | less