Simplest site to site bridged VPN; DHCP requests fail

Discussion in 'Tomato Firmware' started by Steven Johnson, Dec 3, 2018.

  1. Steven Johnson

    Steven Johnson New Member Member

    I have two Linksys routers running Shibby (1.28).
    Server: Basic = TAP, UDP, 1194, automatic, static key Advanced = defaults
    Client: Basic = TAP, UDP, server address / port 1194, automatic, static key, server on same subnet
    Advanced = defaults

    I can't see that it could be any simpler: just bridge every packet between LANs.

    But if I connect wirelessly from my MacBook to the Tomato client, the DHCP request fails.
    If instead I assign a fixed IP address to MacBook, I can ping devices connected to the servers's LAN.
    Or if I enable the client router's DHCP server to assign IP addresses from a pool which does not overlap the VPN server's dhcp pool, the MacBook obtains an expected IP address, and can ping devices on the server's LAN.

    My sense is that DHCP requests (or perhaps any broadcasts) are not correctly bridged from the client's LAN to the server.
    Any remedies? Thx.
  2. Sean B.

    Sean B. Network Guru Member

    Your Macbook isn't supposed to get an IP address from the VPN.. the Tomato client is. The Macbook ( and other connected clients ) should get their IP from the DHCP pool configured on the client router under Basic->Network. The traffic is then NAT'd through the IP address the Tomato client has over the VPN. Same process as going through your WAN IP from LAN ( if subnet is different ). If the DHCP pool on the client router is configured in the same subnet as the other side of the VPN then NAT isn't used.
  3. Steven Johnson

    Steven Johnson New Member Member

    Yes, my Macbook is supposed to get an IP address from the DHCP server running on the VPN server machine.
    And it does, now that I have identified the problem (the client router was not actually running Shibby 1.28; it was running Advanced Tomato). When I switched the client router to a Linksys E2500 running Shibby 1.28, everything worked as expected. The DHCP server on the E2500 shibby client is disabled; my MacBook gets its IP address from the VPN server machine.
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