[Csync2] Syncing through NAT (masquerade)

[Spyros Papanastasiou]

<same mail, unformatted>

Setup:

     Two networks connected through a NAT. The NAT is setup in PC3 using 
$ iptables

         innerPC1 ->.
                     ]-> PC3 (NAT) -> outerPC4
         innerPC2 ->'

Problem:

     "remote host ___ did not accept my identification"

     This happens because NATs work by translating an inner network's IP 
to the router's (and assigning a port for the inner IP).

     In my setup, the rule at fault was:

         $ iptables -t nat -A POSTROUTING -o ${WAN} -j MASQUERADE

     , where "WAN" is the router's interface to the outer network.

Solution:

     Exclusion of csync2 port from Masquerading:

         $ iptables -t nat -A POSTROUTING -o ${WAN} -p TCP --dport 
csync2 -j RETURN

     ! Important: The previous command needs to be put before the 
MASQUERADE one.