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BUG: Unable to connect to modem IP if WAN down

Discussion in 'Tomato Firmware' started by Kevin Darbyshire-Bryant, Jun 24, 2013.

  1. Kevin Darbyshire-Bryant

    Kevin Darbyshire-Bryant Networkin' Nut Member

    Please can someone fix this bug:

    Tested with Toastman or Shibby. When using the 'Route Modem IP' option to be able to connect to an ADSL/VDSL modem connected to WAN port, I'm unable to connect to the modem (ping it even) *IF* the WAN interface has never successfully connected. It looks like vlan2 doesn't get a modem subnet IP address unless the WAN is brought up.

    WAN type is either DHCP or PPPoE.

  2. Elfew

    Elfew Network Guru Member

    Can you debug it, or just test it with Victek latest beta? I cannot confirm it, but I will test it later... no time now, I go sleep
  3. M_ars

    M_ars Network Guru Member

    can confirm that problem/bug. But this behaviour has been around for a while... donĀ“t know if it ever worked "right". If WAN is up, everything is working :)
  4. szpunk

    szpunk Addicted to LI Member

    Confirm that bug too. And this behaviour has been around for a while...
  5. mstombs

    mstombs Network Guru Member

    I don't have this bug with tomato and dhcp- because modems operate in a half-bridge type mode, when they are not connected they still connect to router with a local IP/ short lease.
  6. Kevin Darbyshire-Bryant

    Kevin Darbyshire-Bryant Networkin' Nut Member

    My modem operates in full bridge mode, encapsulating Ethernet frames in RFC1483(IIRC) AAL5. It maintains a fixed IP address for configuration via a web interface for which it doesn't forward those frames. Tomato says 'Route Modem IP' which is great. Unfortunately it is dependent upon Tomato's WAN connection being established. If it's not established then I can't communicate with the modem, to fix what may be a configuration issue (Encapsulation Style (VCMUX/LLC) & VCI for example) which is preventing me from getting a WAN connection....see catch 22 :)
  7. Holy_Hunter

    Holy_Hunter Networkin' Nut Member

    This still seems to be a problem with tomato...
    Im using the latest shibby version for my N66u (140.k26.usb.vpn64k) with pppoe and route modem ip option.
    If the wan goes down and i try a reconnect and it fails i loose access to my modem gui. :(

    wan up:


    Has anyone figured out how to fix this ?
    Is there any workaround ?
  8. Sean B.

    Sean B. LI Guru Member

    Think about it for a second. If your WAN goes down you lose connectivity to the modem, which is connected via your... WAN port. If the interface of which provides the route out of the WAN port goes down it will take your modem connectivity with it. This is not a Tomato bug, it's a fact of routing. PPPoE is a connection within a connection, and it's the one that carries your routed packets. When that connection drops so does the ppp0 interface, which has the route to your modem. You could add the route to the vlan2 interface manually when the PPPoE connection dies and see if that works. If so, automation with a custom script would be a possibility.
    Last edited: Nov 14, 2017 at 12:11 PM
  9. Holy_Hunter

    Holy_Hunter Networkin' Nut Member

    I tought there might be an option for a second virtual wan which survives the static route to my modem even if pppoe fails to reconnect.
    No idea how to realise this with a custom script, if i restart the the router i can access my modem even if pppoe doesnt connect so i guess it must be possible...
  10. Monk E. Boy

    Monk E. Boy Network Guru Member

    You would need to have two IPs assigned to your WAN port, one for normal internet connectivity, another static solely for connecting to the modem. Remember to block traffic being routed out the static IP, especially if the other IP is down. And be sure to never route traffic out the static IP if the other IP is down... probably not defining a gateway for that IP would do it. And you want one of the interfaces to use PPPoE...

    But how to do this under Tomato? Hell if I know. Remember, Tomato's OS isn't Linux, it's Linux-like. In Linux it's not all that complicated:

    There's probably a reason this problem is still outstanding.
  11. Sean B.

    Sean B. LI Guru Member

    When you reboot, and prior to the ppp0 interface making a connection, the route to your modem is likely on the vlan2 interface as it would be with a non-pppoe connection. Once ppp0 becomes active the routing table is changed, and probably doesn't change back when the connection dies because it has to remain in order for pppoe reconnect attempts to be tried/work.
  12. Sean B.

    Sean B. LI Guru Member

    @Holy_Hunter , when your connection dies and the WAN goes down have you tried simply bringing vlan2 back up? If not, give it a try.. GUI - Tools->System Commands and run this:

    ifconfig vlan2 up
  13. Holy_Hunter

    Holy_Hunter Networkin' Nut Member

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