[vserver] iptables rules for lo interface in guest

Hi All,

previous install on xen was using iptables to redirect posgreslq port
( 5631) to different port :
-A PREROUTING -p tcp -m tcp --dport 5631 -j REDIRECT --to-ports 5666
-A OUTPUT -p tcp -m tcp --dport 5631 -j REDIRECT --to-ports 5666

when migrated to virtual server use rules on host to redirect port:
-A PREROUTING -d $EXTIP/32 -i eth0 -p tcp -m tcp --dport 5631 -j DNAT
--to-destination $GEUSTIP:5666
which working OK for any outside access but not for localhost in guest.
so I am a bit confuse how properly apply iptabels on host so it will
work for lo in guest?
Tried tcpdump - it will show like guest ip like 127.111.0.1 applying
it as source or dst in iptabels doesn't help.

-- 
--
Michael