[LARTC] load balance/redundancy

[Paul hesselsp@sheridanc.on.ca]

<PRE>Arthur,

Thanks for your help.  I tried what you suggested, here is the result:

# /sbin/ip route add default nexthop via 24.141.xxx.1 nexthop via
64.229.xxx.1
RTNETLINK answers: Network is unreachable

So instead, I tried:

# /sbin/ip route add default nexthop via 24.141.xxx.1 dev eth0 nexthop via
64.229.xxx.1 dev ppp0

# ip route ls
64.229.xxx.1 dev ppp0  proto kernel  scope link  src 64.229.xxx.12
24.141.xxx.0/22 dev eth0  proto kernel  scope link  src 24.141.xxx.89
127.0.0.0/8 dev lo  scope link
default
        nexthop via 24.141.xxx.1  dev eth0 weight 1
        nexthop via 64.229.xxx.1  dev ppp0 weight 1

and that seemed to work, so I tried:

# /sbin/ip route add default nexthop dev eth0 nexthop dev ppp0

# ip route ls
64.229.xxx.1 dev ppp0  proto kernel  scope link  src 64.229.xxx.12
24.141.xxx.0/22 dev eth0  proto kernel  scope link  src 24.141.xxx.89
127.0.0.0/8 dev lo  scope link
default
        nexthop dev eth0 weight 1
        nexthop dev ppp0 weight 1


Now this seems to work.  Is there anything wrong with this?  Can you take
a guess at why what you suggested didn't work?  I think I tried all the
different permutations with addresses, I think the problem must come from
the pppoe interface.

Now all I have to do is kludge something together for my redundancy, set
up firewalling, and masqerading.

Thanks,
Paul


On Sun, 10 Dec 2000, Arthur van Leeuwen wrote:

&gt;<i> On Sun, 10 Dec 2000 <A HREF="mailto:hesselsp@ashaman.dhs.org">hesselsp@ashaman.dhs.org</A> wrote:
</I>&gt;<i> 
</I>&gt;<i> &gt; Well, I think I have the redundancy down... In a kludgy way.  Right now I
</I>&gt;<i> &gt; have two default routes.
</I>&gt;<i> 
</I>&gt;<i> &gt; route add default gw 24.141.xxx.1
</I>&gt;<i> &gt; route add default gw 64.229.xxx.1
</I>&gt;<i> 
</I>&gt;<i> Actually, if I understand the code correctly what you do here is in fact
</I>&gt;<i> create a multipath route. A cleaner way to do so is using ip route 2 as
</I>&gt;<i> follows:
</I>&gt;<i> 
</I>&gt;<i> ip route add default nexthop via 24.141.xxx.1 nexthop via 64.229.xxx.1
</I>&gt;<i> 
</I>&gt;<i> This explicitly states that you will be using a multipath route and balances
</I>&gt;<i> outgoing routes over the two interfaces.
</I>&gt;<i> 
</I>&gt;<i> &gt; I can write a script that if one of connections goes down for x number of
</I>&gt;<i> &gt; pings, then remove the route.
</I>&gt;<i> 
</I>&gt;<i> And here's the crux. It would be nice for the kernel to use its idea of
</I>&gt;<i> gateway reachability (in the neighbor cache) to automatically ignore an
</I>&gt;<i> upstream hop in case it is dead. However, for multipath routes, no
</I>&gt;<i> death detection is done on the gateways in the different hops. This is
</I>&gt;<i> quite somewhat different from the single default route behaviour 
</I>&gt;<i> 
</I>&gt;<i> &gt; Now for the load balancing.
</I>&gt;<i> 
</I>&gt;<i> The kernel balances outgoing routes over the upstream interfaces. Unless all
</I>&gt;<i> your packets go to the same address, that should balance your traffic
</I>&gt;<i> already. Other than that there's some code based on EQL that will flush the
</I>&gt;<i> route cache after every packet, thereby smashing the route-balancing down to
</I>&gt;<i> packet-level load balancing. I can't seem to find the URL for that code,
</I>&gt;<i> though, unfortunately.
</I>&gt;<i> 
</I>&gt;<i> &gt; Can you point me to documentation on iproute?  Other then the Advanced
</I>&gt;<i> &gt; Routing HOWTO, unless I am missing something in it.
</I>&gt;<i> 
</I>&gt;<i> <A HREF="http://snafu.freedom.org/linux2.2/iproute-notes.html#doc">http://snafu.freedom.org/linux2.2/iproute-notes.html#doc</A>
</I>&gt;<i> 
</I>&gt;<i> There's some more interesting stuff on <A HREF="http://snafu.freedom.org/linux2.2/">http://snafu.freedom.org/linux2.2/</A>
</I>&gt;<i> as well. 
</I>&gt;<i> 
</I>&gt;<i> Doei, Arthur.
</I>&gt;<i> 
</I>&gt;<i> 
</I>
-- 
HEY!  I'm a guy like me!

		--Homer



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