Got an interesting problem. I have a solution, but it's horribly clunky, so I wonder if anybody knows a better way of doing it.
I have a RouterBoard with two IP addresses and two gateways, let's call the IPs 126.96.36.199 and 188.8.131.52 and the gateways 184.108.40.206 and 220.127.116.11
Everything beyond the RB is completely out of my control.
I need to create two L2TP tunnels from the RB back to the same IP on an LNS outside on the Internet somewhere.
When creating an L2TP tunnel, there doesn't seem to be any way of specifying which source IP (i.e. 18.104.22.168 or 22.214.171.124) to use - if I could do this, then routing rules would permit routing the correct tunnel through the correct gateway. The only thoughts I had were specifying 'Local address' in the PPP profile (but that doesn't appear to change the source address) and 'outgoing filter' (but this only appears in the filter not the mangle table).