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  • Using NIC teaming with multiple ISP connections

    Hi there,

    Forgive me for asking this - I could be missing something obvious - but I'm new around here, and am trying to work out if this is possible.

    I'm about to install a Server 2012 R2 server in the office here. The building has quite a nice infrastructure - it's fully network cabled, is running multiple Cisco switches in the server room, and currently has a couple of servers already installed and running, to handle cameras, phones, etc. Everything's already set up for me to simply drop the server in place, hook it up to a switch, assign it a fixed IP address and we're good to go. There's only one small fly in the ointment, that no-one told me about - the internet speed on-site is abysmal. Truly terrible, and thanks to where the office is, we can't get any better than we currently have.

    This lead me to think about line bonding and suchlike, and my actual question: Since the server I have has two NICs built-in, and we could add another DSL line on the premises alongside the current one, would it be possible to hook up a second DSL line (via their supplied router/modem) to the second NIC in the server (the first NIC hooked up to the switch, and the rest of the network) and use the new NIC Teaming option to balance the load across both connections?

    I'm aware that if - say - we had 2 x 50mbit download/25mbit upload lines and this worked, it still wouldn't allow me to (for example) download a file at 100mbit speed; I'd assume that it would allow two users to download a file at 50mbit speed each, and generally alleviate the congestion that they're going to face by using one slow net connection. Or that's the hope!

    Is this something that the NIC Teaming option would allow? Or am I misunderstanding the technology? Any advice and insight would be gratefully received

  • #2
    Re: Using NIC teaming with multiple ISP connections

    not something that's going to work easily and simply unfortunately.

    you need a way to make sessions stateful (through one link or the other) otherwise everything's going to get well confused:

    ComputerA sends download request to InternetA via NIC1
    InternetA receives traffic, sends traffic back to ComputerA via NIC1.
    ComputerA sends Ack, requests next stream to InternetA, traverses NIC2.
    InternetA goes "WTF, I expect traffic from NIC1"

    (That's a really poor way to explain it, actually.. but you get what i'm trying to say I hope.)

    you'd also then need to have your new server doing NAT.


    Ideally, what you would do is:
    - add a new core router/firewall
    - attach two ADSL services (or whatever)
    - define policy based routing, so that particular traffic always traverses one link, while other traffic traverses another.
    - also define SLA trackers or whatever they are, so if one link goes down, it will automatically fail over

    your policy routing can be based on all sorts of things like source, destination, protocol type, source and destination, source and protocol, etc etc


    this is all "on-paper" as well - i'm not sure what this particular server is tasked to do, how it fits into your infrastructure etc.
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    • #3
      Re: Using NIC teaming with multiple ISP connections

      Originally posted by vedekandy View Post
      This lead me to think about line bonding and suchlike, and my actual question: Since the server I have has two NICs built-in, and we could add another DSL line on the premises alongside the current one, would it be possible to hook up a second DSL line (via their supplied router/modem) to the second NIC in the server (the first NIC hooked up to the switch, and the rest of the network) and use the new NIC Teaming option to balance the load across both connections?
      The short and simple answer is "no." Bonding is a layer 2 function: Two (or more) network interfaces act as one on some level, for the purpose of load balancing and/or fault tolerance.

      In order to make use of two ISP connections, you'd have to lo load balance at the network (IP) layer. This would typically involve running the BGP routing protocol and peering with two ISPs. You can't just aggregate two ordinary ISP uplinks, as they will each usually have a single, public IP address behind which you're supposed to "hide" (NAT) your outbound traffic.

      Some routers do explicitly support this kind of setup (load balancing without BGP), but the load balancing is then done on a per-host basis. Otherwise, to outside servers it would appear that your internal hosts were switching their IP addresses at random, which in turn would probably break quite a few web sites and other applications.

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