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WDS with 2 ADSL gateway, automatically switch to another when one is down.

Discussion in 'Tomato Firmware' started by bingjiw, Nov 14, 2008.

  1. bingjiw

    bingjiw Addicted to LI Member


    Is this WDS topology below possible? What if with enable or disable the STP ( Spanning Tree Protocol )?

    Code:
    ADSL#1       ADSL#2
      |            | 
      |            |
     AP#1        AP#2
        \        /
         \      /
          \    /
           AP#3
    When AP#1 and AP#2 are both fine and connected to internet, the AP#3 will use AP#1 by default to connect to internet, is it possible?
    Is it possible that AP#3 can use both AP#1 and AP#2 simutaneously to provide internet access?

    If the AP#1 is down, the AP#3 will automatically use AP#2 and connect to internet, is this possible?

    If the AP#2 is down, the AP#3 will automatically use AP#1 and connect to internet, is this possible?

    If the modem of ADSL#2 is down but AP#2 is fine, will the AP#3 automatically use AP#1 and connect to internet, right?

    How to config the three APs to automatically accomplish these tasks when in these different cases above?

    Regards,
    Bingji

     
  2. HennieM

    HennieM Network Guru Member

    Your setup has little to do with the functionality of WDS, but everything to do with routing.
    You don't need the WDS parts if you only want to use either ADSL1 or ADSL2 as routers to the internet. I'll assume you need the WDS links for this discussion.

    To ensure the best redundancy, a 2 part process should be followed:

    Part 1: Make sure the WDS links are redundant.
    This is the easy part. Set up all 3 your APs as "AP+WDS", and everyone links to 2 other WDS nodes; that is
    AP1 should be WDS linked to AP2 and AP3
    AP2 should be WDS linked to AP1 and AP3
    AP3 should be WDS linked to AP1 and AP2
    so you have this
    Code:
    ADSL#1       ADSL#2
      |            | 
      |            |
     AP#1-------AP#2
        \        /
         \      /
          \    /
           AP#3
    You should now definitely have STP on on all APs, as you can have more than one path:
    to get from AP1 to AP2, traffic can go directly to AP1--AP2, or traffic can go AP1--AP3--AP2.
    If you don't have STP on on all devices, you will get loops in the network that could (and probably would) bring the whole network down.

    Part 2: Sort out routing.
    This is the difficult part to do properly with load balancing (simultaneously using ADSL1 and ADSL2 for internet access). The easiest way of sort of accomplishing what you want, is to specify both ADSL1 and ADSL2 as routers (or default gateways) to your PCs. (As mentioned above, you can do this whether you have the WDS setup or not).

    Say ADSL1 is at 192.168.1.1, and ADSL2 at 192.168.1.2. Now, you specify, via DHCP, or by static configuration, the routers on your PCs as 192.168.1.1, 192.168.1.2 (in that order).

    Your PC now wants to get to the internet, so it will try to send internet traffic to 192.168.1.1 (ADSL1). If ADSL1 is up and running, your PCs will keep sending internet traffic via ADSL1 and never through ADSL2. However, if, after a while, a PC gets no reply from 192.168.1.1 (because ADSL1 is down or something), it will try to send the internet traffic to 192.168.1.2 (ADSL2), and volla.
     

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