Re: [LARTC] load balance/redundancy

Linux Advanced Routing and Traffic Control

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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:

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

-- 
HEY!  I'm a guy like me!

		--Homer




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