There's a company (B2B interface) that provide certain services through a custom ISP (DSL), but this limits the internet connection only to this site, and on the office we have an regular ISP (DSL) that gives internet access to all computers.

We want to run 2 modem/routers, and connect them, and give access to the internet to all computers, but when they reach the specific site , route the traffic through the other ISP (modem) instead of switching from wireless/physical network each time, not sure what options I can have (there's no problem to add entries on the hosts file (windows clients) to change the domain to a specific IP). Not sure if routing tables is the way to go, or there's any way to define a kind of proxy.

The modem that is currently connected to the internet is D-Link DSL 6850U, the other is still not there (if some model specific or feature is needed we can buy it)


  • 4
    You should consider getting a commercial-grade router that allows you to make changes to the routing table so that you can direct traffic as needed. Routers like the D-Link are consumer grade, and questions about those are off topic here.
    – Ron Trunk
    Commented Apr 24, 2017 at 12:55
  • My main question is what is the kind of settings/features are needed for that purpose, is routing? can I do routing depending on the request (not the IP/MAC generating the request) ? the modem model was only as reference.
    – ABens
    Commented Apr 24, 2017 at 15:22
  • You will need interfaces for both connections, static routing, and possibly network address translation.
    – Ron Trunk
    Commented Apr 24, 2017 at 15:24
  • You can route traffic to a specific gateway using host routes in each endpoint (computer) but this is usually accomplished in the network equipment using policy routing. Commented Oct 22, 2017 at 0:02
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Commented Feb 21, 2018 at 16:39

2 Answers 2


You can do outbound routing to specific destination with static routes. You can prefer one of ISPs for particular site inbound with BGP and your own PI pool. You can do advanced routing decision with some L4-L7 technologies, for instance, Cisco PfR. Though I can't see a good way to reroute through another ISP after connection to remote site is established, if I understood your intent correctly.


This sort of thing is possible but not easy in the general case.

The first problem is how to split traffic. If the provider of "special services". If the destination IP addresses for the "special services" are well-known and don't conflict with resources you need on the public Internet this is easy, just use static routes. IF they are not well known or there is an addressing conflict then life will get far more painful.

You will also want NAT so that the source address used is correct for the network the packets are sent over.

The second issue is DNS, assuming the special services are not in the public DNS and the DNS for the special services won't resolve public hostnames you will need a local DNS server that is smart/configurable enough to forward queries to the right place. may prefer other soloutions.

  • The services are on specific website that is also available to the public (but in a simpler interface), so as I understand is possible to make a route to a specific IP independently of the source machine. Regarding NAT if is only a web site there's a need for it? DNS I can solve with host file in windows clients (11 machines, so not so hard to set up) . Does it make sense?
    – ABens
    Commented Apr 24, 2017 at 19:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.