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:
Customer attempts to make firewall changes from vCenter VAMI ends up losing access to vCenter.
This could happen if customer entered wrong IP, block complete subnet range, or mistakenly enable the iptables service 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