Two gateways, how to route?



  • Hello,

    I've studied networking a long time ago and have been working with it off and on for years, but I never really got into the more advanced stuff because our typical setup is so simple. I now want to brush up on my knowledge but got stuck on a little problem that I hope someone here could help with.

    Lets say I have a network (10.10.10.0/24) with two routers;
    10.10.10.1 (default gateway)
    10.10.10.2

    If I would like to use 10.10.10.2 as default gateway I would simply change the default gateway on the desktop clients and it would work. But what if I would like them all to use 10.10.10.1 as default gw and then from that gw route some traffic through 10.10.10.2?
    I guess it would make more sense if you took IPSec as an example. If 10.10.10.1 was the internet gateway and 10.10.10.2 was the IPSec router, and you wanted to route traffic to the LAN's behind the tunnel without editing default gateway of the clients - is that possible?



  • Use a transfer network between the routers and set a static route on the default gateway to route specific traffic to the other router.
    Also set a static route on the 10.10.10.2 router to route the network 10.10.10.0/24 which is behind 10.10.10.1 back.


  • LAYER 8 Global Moderator

    "Lets say I have a network (10.10.10.0/24) with two routers;
    10.10.10.1 (default gateway)
    10.10.10.2"

    You would never have such a setup, not in any real network..  Such a setup would mean the client is actually sitting on the transit network..  Routers are connected via transit or as viragomann calls it a transfer network..  If you have a client sitting on a transit network unless your doing routing on the host your going to run into asymmetrical routing.

    If the IP you get from ISP is really just a transit network between your router and the ISP router.. Now they might have lots of downstream "routers" connected to this transit - ie the customers but in reality its just a transit..

    If you had a router that connected to ABC network(s) and another router that connected to XYZ network(s) and you wanted a client that hangs off 1 router to be able to use the other router to get to those networks then you would connect the routers together with a transit and you would either setup routes between the routers so they know when to talk to the other router to get to 1.2.3.4 or you would let them exchange the networks they can get to via a routing protocol..

    See attachment - might help to visualize a transit/transfer network




  • Like I said, it's just hypothetical, trying to understand some things.

    I usually build networks with only 1 router, and let the physical devices like switches, ap's and such be in a backbone network (vlan1) while the devices and clients are on other vlans. But what if I want to offload a modest router that is being used for some high throughput backups for example, by adding a second router just for that purpose.

    I guess transfer network would be a solution, yes. Will consider that in my scenario. Thanks!


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