iptables rules

[Jörg Harmuth]

Peggy Kam wrote:
> Hi,
> 
> I have defined the following firewall rule in iptables:
> 
> iptables -I FORWARD -s 192.168.22.102 -d 192.168.1.112 -p tcp -m tcp -m
> multiport --ports 22,23,24,25 -j ACCEPT
> 
> why were the packets able to get to 192.168.1.112 on port 22 when the
> packets does not even come from ports 22,23,24 or 25?

man iptables:

--ports [!] port[,port[,port:port...]]
               Match if either the source or destination
               ports are equal to one
               of the given ports.

So, this is expected behaviour, provided that there are no other rules 
in the way.

HTH,

Joerg