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I have LAN_1 and LAN_2 interconnected with an openvpn tunnel terminated ona pair of SOHO routers running busybox.

One of the vpn purpose is to allow clients on both LAN_1 and LAN_2, to administer the two routers themselves, so telnet/ssh connection must be established from every client to every router. telnet/ssh daemons work fine - when client_1 connects to router_1 in LAN_1 it works, same for client_2 to router_2 in LAN_2. Problems arise when the TCP connection crosses the vpn tunnel. The weird thing is that if (server_X is a generic host accepting connection in LAN_X):

  • openvpn is in bridged mode (tap), client_1 -> server_2 ok, client_1 -> router_2 ok,
  • openvpn is in routed mode (tun), client_1 -> server_2 ok, client_1 -> router_2 KO: receives a TCP RST when trying to connect to both telnet/ssh and the connection is dropped.

I'd really like to set openvpn in routed mode because I don't want L2 garbage to burden the lousy ADSL uplinks but so far it's not an option because i need to be able to access the router mgmt daemons. Any experiences on such an issue? here is the wireshark trace. I don't know much about TCP RST, maybe openvpn routed messes up with busybox socket handling?

thanks g.

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Most likely there are firewall rules in router_2 that prevent SSH access from the IP address space used by the routed mode tunnel

Check the firewall in router_2.

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