l2tp/ipsec issues

RouterOS General
1

I have setup L2TP/Ipsec client connections for “road warriors” with the Windows Built-In client and it works okay except:

  1. I’ve discovered two such VPNs running on the same remote local network won’t work. I’ve read here that the protocol just doesn’t allow it.
  2. I can live with scheduled use of the one connection available, but when one client disconnects, the other can’t connect. Rebooting the failing machine fixes the problem, so I presume it’s something local and not in the router. I think that if a second VPN tries to connect, it is given the one available and the loser is left in a confused state that keeps it from working again without a reboot. I’m sure a full reboot is overkill, but I haven’t found the magic command to clear the issue.
2

The best way out is to switch to IKEv2. You can implement this workaround to allow multiple L2TP/IPsec clients to connect from behind the same NAT, but it only makes sense if you really need the L2TP/IPsec for some reason. The reasons why IKEv2 is a better choice are mentioned in that topic too.

Regarding the reboot of the other client - you may need to give some time to the firewall and the IPsec stack at the Mikrotik side to “forget” the previous connection, which may take minutes. So maybe it would be sufficient to wait for 10 minutes after the first client disconnects before attempting to connect the second one.