Is it possible to connect TWO ADSL2+ Modem Routers together?

By numibesi
May 11, 2006
  1. Hello there,

    First of all, this is my first post here, i hope to be helped and help as mutch i can in the forum. :]

    This is the situation,

    I own a Lan-House with 20 computer connected to a Draytek 2600 plus Router, and an ADSL connection U/D: 416Kb / 4096Kb.

    Currently i'm having major problems with my ISP connection, i'm portuguese and here in Portugal, like in other countries of the world, we have 2 or 3 companies that monopolize the internet access, but regardless that situacion we have "crapy" connection regarding the velocities, in best we have 16 MB Downstream and 512 Kb upstream, as some of you can imagine, and by doing a simple math operation:

    -> (4096/8)/20= 25 KB to each pc downstream
    -> (512/8)/20= 3.2 KB to each pc upstream​

    this is far but far from a normal and regular connection that each one of us have in our home. To control this i must have a Bandwith-Control software to that one user does not use all the bandwith and the other cannot use it.

    So i came up with one solution, since i can't have higher speads unless i subscrive to a Dedicated Line ( very but very expensive), i have decided to contract two ADSL lines to a difrent operator that offers me 2 lines of U/B: 512Kb/4096Kb each.

    My problem is, i have to ADSL/Modem Routers that are connected each one to the appropriated adsl line, now:

    Is it possible to connect them directly to each other?

    I know that i can connect them using a Load Balancing Router, but in order not to buy any more equipment i wonder if it is possible my first question.

    I apreciate all of you the time you spent reading this question, and in advance your reply's.

    Thanks once again,

    Nuno Simões

    PS: And by the way sorry my english i know i type with lots of erros. :)
  2. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    Sure, you can connect the two modems to each other no problem. No, you cannot make them share their bandwidth :) You need some kind of load balancer for that.

    A crude solution would be to make half of the clients use one router and the other half the other as a gateway. Or, if the routers' netmask allows, set up the default gateways (routing tables on the clients) so that half of the traffic goes to router #1 and the other to router #2
  3. numibesi

    numibesi TS Rookie Topic Starter

    Thanks for yor reply, the "split" of the machines between the two routers was my first thought, but it fails on one part, due to the "time managemente" software the server machine must be connected to all computers to allow the access of the clients, explaining better:


    meaning that, using your solution i would have something like this correct ?!


    If i connect the two routers to each other is the same has having a switch, since they will not double the badwith has expected but will only work as a fail/safe connection, if the first router loose the conn the second one will sustain it.

  4. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    You can connect the ethernet physically no problem.

    You "split" the machines in the sense that half of them will use router #1 as the gateway and the other half will have router #2 as the gateway. All machines will still be able to communicate with each other.

    You will have to use static IP setup for this of course. First, set the LAN addresses of the routers to be different - and for example. Disable DHCP services on both souters. Connect both routers to each other either directly or through a switch - doesn't matter.

    Now configure half of your computers with addresses, say 100-199 and the gateway/DNS .1 and the other half as 200-254 and gateway/DNS .2.
    This is rather clumsy, but it will work.

    If you are feeling extra cool, add the other router as the second gateway/DNS to all the computers. So that 1xx computers have .1 as the first gateway/DNS and .2 as the second; 2xx computers have .2 as the first gateway/DNS and .1 as the secondary. This way all the computers will switch over to the other router in case of a breakdown.

    An ugly ASCII drawing..
              Router1          Computers
              /       \         /
    Internet--         --Switch?-Computers
              \       /         \
              Router2         Computers

    Now, since you have that many computers, I assume you have some switch somewhere? If it is something advanced that supports VLANs, then you could set up something more elegant.
  5. numibesi

    numibesi TS Rookie Topic Starter

    Yes in case due to the physical size of the store, i have in fact, 4 switchs.

    I havent thougt or understood your idea of connecting them in that way. Of course in that situation there will be no problem to the time Server Machine to work, since they will be all on the same network.

    Thank you very mutch for your replys and help.
  6. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    It's not that difficult.. You just have to know that ethernet (the cables) and IP (the internet access) are on different levels.

    Think of it as roads and cars.. The road network goes everywhere, but the traffic rules tell the cars to take only specific routes - you are supposed to drive only on your own side of the road, you can't go in the wrong direction through highway exits, you are allowed to cross country borders only through special sites etc.

    Just thought of another cool solution..

    Leave the DHCP on both routers enabled. Make the DHCP address range on the routers to 100-110 and 200-210 respectively. Set the IP information on the computers to automatic.
  7. numibesi

    numibesi TS Rookie Topic Starter

    Unfortunately i can't work with DHCP :(,

    The time management progrem need static IP access to control the clientes, like this,

    Station 1:
    Station 2:
    Server 1:

    and so on.

    If i use DHCP, depending on the Boot of the computers i could have for example Station 1 with IP, so i had to change the IP of the stations on the program every day and check one by one the IP that was assigned each one. So i assigned every station is own and private IP. :)
  8. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    You know, DHCP addresses are pretty static actually. When you start up a computer, it requests for the IP address it got the last time. And the server starts recycling IP addresses only when it has used up all the free ones.
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