Re: Multi-Homed Routing

From: Charlie Root (root_at_energistic.com)
Date: 08/29/03

  • Next message: Sten Daniel Sørsdal: "RE: Multi-Homed Routing" 
    Date: Fri, 29 Aug 2003 15:17:32 -0500
To: "Lapinski, Michael (Research)" <lapinski@crd.ge.com>

    On Fri, Aug 29, 2003 at 03:18:41PM -0400, Lapinski, Michael (Research) wrote:
    > Are you using a fbsd box as a router?
    >
    > if no, you need to configure BGP on your border router.

    True that.

    > if yes, yuck, routers route, server's serve. =)

    True but an OS is neither a router nor a server. Its just an OS. The use
    you put it to defines if the box is a router or a server (or both).

    > I have recently added a 2nd Internet source (for redundancy) and I want to
    > know how to make FreeBSD choose a primary outbound internet source, and
    > chose the other if the primary is down?

    You'll need to be running a routing protocol. Your standard routing
    table probably isn't going to serve you very well. If aren't able
    to exchange protocol with your upstreams (usually with BGP) then you'll
    have to get clever with DNS tricks and route manipulation.

    Are you getting IP space from both providers? Are all services setup
    to listen on both subnets? Does your DNS point to both subnets? If one
    subnet goes down does DNS stop pointing to the bad subnet (only half a
    cure because the now bad subnet IPs are probably cached out there on the
    net somewhere anyway).

    The common situation is to advertise via a dynamic routing protocol such
    as BGP4 your IP space to both of your upstreams. This isn't really possible
    if your upstreams are DSL, cable or small-time wireless providers.

    > Am I correct to assume that FreeBSD will automatically return incoming
    > requests back through the interface that it arrived on?

    Ummm... no. I don't think you are. FBSD will likely send that packet
    back out whichever interface is labeled 'default' or, in the case of
    dynamic protocols, whichever route has the lowest metric back to the
    destination.

    -Steve

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  • Next message: Sten Daniel Sørsdal: "RE: Multi-Homed Routing"

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