I'm curious, what Router OS are you using?
Debian Wheezy with backport kernel 3.16 Also Raspbian Wheezy with kernel 4.1.19+
Well, it probably is some setting. It has worked before but lately I have not seen any RIP packet in the iptables counters, even though I see them with tshark.
Now I just use -r and that works. Not worth to spend effort on.
Rob