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WRT-54G with PPPoA

Discussion in 'DD-WRT Firmware' started by roddyboy, Jun 17, 2007.

  1. roddyboy

    roddyboy LI Guru Member


    I'm trying to run my Linksys WRT-54G DD-WRT router with my PPPoA ADSL connection. I have a modem doing the modeming of the signal, and it's running in half-bridge mode so the Linsys gets allocated the WAN IP. The half-bride is working fine, as if I connect my computer to it I get allocated the WAN IP and I can browse the internet fine. However, when I try plugging the Linksys in, the PPP connection drops reasonably quickly and won't reconnect. I'm wondering if this may be a NAT issue, I can't seem to find any settings for NAT in the Linksys.

    This is what my modem's log shows for when I unplugged myself from the modem (in half bridge mode), and plugged the Linksys in. It seems the PPP session dropped almost straight away too.

    1 06/17/2007 16:25:57> Firewall received interface change notice.
    2 06/17/2007 16:25:57> PPP1 Session is down.
    3 06/17/2007 16:25:57> DNS: Remove IP address (Auto discovered)
    4 06/17/2007 16:25:57> DNS: Remove IP address (Auto discovered)

    I went and had a look at the firewall settings on the modem, and it said "Firewall is not active when in half bridge mode"

    I'm using a Linksys WRT54G v5, DD-WRT micro v23SP2.

    Thanks in advance for any help.

  2. mstombs

    mstombs Network Guru Member

    Check the IP address, netmask and gateway the router is getting. Half bridge can play tricks with netmask and gateway, sometimes this 'spoofing' cannot work as the IP and gateway are so different. Windows XP and recent Linux had no problem with a gateway not in the same network mask as the IP address, but stock Linksys and derived Hyperwrt Thibor and Tomato don't know how to handle without an extra bit of help with a firewall script





    for solutions

    Is something similar needed for dd-wrt, or maybe the router is just trying to connect with pppoe should be dhcp?
  3. roddyboy

    roddyboy LI Guru Member

    Hi thanks for the reply.

    I'm having a look through the posts you linked me to, a lot of it is gibberish to me, looks like this'll be a bit of a learning curve for me.

    I have it connecting via DHCP, my connection doesn't support PPPoE.
  4. mstombs

    mstombs Network Guru Member

    Note: I don't know dd-wrt micro at all, and haven't used dd-wrt for some time so don't know what is now available in terms of wanup scripts etc.

    I don't understand why router should tell modem to disconnect, usual problem is just that surfing doesn't work - so could be leading you up the wrong path - sorry!

    Watch out for a lot of miss-info on PPPOA bridging in UK, a number of people can use PPPOE full bridge because PPPOE is supported but not advertised.
  5. roddyboy

    roddyboy LI Guru Member

    Yeah it's definitely strange that the PPP connection is dropping. I'll have a hunt around anyway. It's exam time for me at the mo so probably won't have a good look for a few days.

    There is no PPPoE support where I am, I can assure you of that. New Zealand is the most backward country in terms of telecommunications.
  6. roddyboy

    roddyboy LI Guru Member

    Ok so I've had all my exams and have a week before I start uni again now, so I'm ready to try to tackle this and see if I can get it working.

    It seems from what I've read that the Linksys can't handle the IP and Gateway being on a different network masks, as mentioned in this thread. Is it possible to fix this issue using the routing function on either the Linksys or the modem?

    Routing pages:
  7. mstombs

    mstombs Network Guru Member

    Have to admit I don't know how to interpret the dd-wrt/modem web page route, but here is my Linksys router running Tomato with a half-bridge modem. Tomato has to be helped to understand the IP/Gateway netmask issue with the firewall script I developed under Hyperwrt here:-


    # route
    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    89.240.xx.y     *      UH    0      0        0 vlan1     *        U     0      0        0 br0       *            U     0      0        0 lo
    default         89.240.xx.y         UG    0      0        0 vlan1
    89.240.xx.y is my current ISP Gateway

    Your modem routing doesn't show the half-bridge connection (my examples in the linked thread) it only shows a local network on br0.
  8. vegaman

    vegaman Guest

    My routing table is similar to mstombs, I just ssh in and set it up manually. I'm in New Zealand too, and my "modem" (for lack of a better word) doesn't support half-bridge mode, so I have to set up the routes manually on there too. Though I have a Static IP so it's possibly a slightly different setup.

    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    203.109.xxx.yyy *      UH    0      0        0 vlan1     *        U     0      0        0 br0       *            U     0      0        0 lo
    default         lo2.akl-grafton         UG    0      0        0 vlan1
  9. mstombs

    mstombs Network Guru Member

    Cool - so likely dd-wrt has the same issue as Hyperwrt and dd-wrt if IPs assigned dynamically, and same wan port label? Same origin in Linksys GPL code I guess.

    I had to re-invent the modem routing as well - for my modem that didn't have a half-bridge mode - but runs Linux! Details I guess you will recognize in the first post in this thread

  10. ivabigbut

    ivabigbut LI Guru Member

    My own problem seems similar, tried to use a speedtouch modem / router connected to a DD-WRT for wireless networking side of things and also
    my isp only supported PPPoA, setting the speedtouch to bridge mode there were
    no options for PPPoA so I eventually reset speedtouch to factory defaults doing
    all the routing and turned the DD-WRT into a switch following the instructions


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