[LARTC] Multipath routing for beginners ...

["Sebastian Bleikamp" <Sebastian.Bleikamp@xxxxxxxxxxxxxxxxxxx>]

Hello !

I´ve been "collecting" and reading all mails and articles on equal cost multipath routing for about two month, because I have the possibility to connect to two ISPs over two different devices and want to do some primitive (per-flow based) loadbalancing. But it doesn´t work, or at least I can´t get it working. So it would be really nice if someone could explain me ho to set up ecmp from the scratch.

I am familiar with standard network and routing issues (kernel <2.4.x), masquerading (although I´ve got static IPs), iptables and the new iproute (ip) commands, and know how to use traffic control and sheduling (at least in theory :-) ). I know _nothing_ about RIP, OSPF & routing daemons except their name, use and some principles of work.

My setup is as follows:

 

     *ISP1*           *ISP2*
        |               |
 (ppp0) +---*LinuxBox*--+ (ppp1)
                |
                | (eth0)
                |
   -----+-----+----+----+---- (LAN)
        .     .    .    .

 

 

LinuxBox is connected ...

    through ppp0 to ISP1, address 10.0.1.10,

        gw 10.0.1.1 (1st possible default route)

    through ppp1 to ISP2, address 10.0.2.10,

        gw 10.0.2.1 (2nd possible default route)

    through eth0 to LAN, address 10.0.0.1,

        netmask 255.255.255.0

 

With this setup everything works fine. Both systems know all of my IPs and have routing set correct.

 

Then I tried to set it (ecmp) up like in the examples found on the net, but they didn´t work, and the error was always ths same: When I had finished standard routing and finally used the "ip route add default nexthop ... nexthop ..." command, he accepted it first, but marked one device "DEAD" immediately.

All necessary options have been compiled into the kernel (now 2.4.13).

 

I don´t know what to do and where to look any more - theres no documentation or howto on details of ecmp. It would be really a great help if someone knows something about it.

 

 

 

-=> Sebastian Bleikamp
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