I have a cable modem and a dsl modem on a rb 532...
the dsl is the primary gateway for all 0.0.0.0/0 dest. traffic
i can setup a mangle rule to grab icmp's with a dst ip of the cable modem (the non primary link). I then set it to packet mark routing and give it a name. i then setup a route that says dst (ip of machine doing pining) use gateway of cable modem when you see the packet mark of the mangle rule.
I can see the mangle rule, sees my pings from a external MT router (different part of internet). but they do not route back.
if i simply remove the packet mark part of the route it works and the pings properly go back out across the cable modem (due to the dst. rule of the route)
any ideas? am i doing something to cause the route not to see my packets being marked by the mangle rule?