Sorry I missed this part: >>>What is the meaning of: echo 0 > /proc/sys/net/ipv4/conf/eth1/rp_filter I think it disables the reverse path filter for that interface (eth1). Now you might ask, what is the reverse path filter? And I don't know! Apparently it does this: > # prevent incoming packets on masqueraded connections from being dropped > # as "martians" due to the destination address being translated before the > # rp_filter check is performed However, when I commented out the line it made no difference so I've left it there for people to comment back in if they find they have problems as described. Regards, Matt.