[LARTC] Multipath routing

[Michał Margula]

Piotr Chytla pisze:
> First of all equal cost multipathing is evil ;>, It simply doesn't work for packets in
> forwarding path besides support in kernel is not maintained
> 
> Realy if you want load balance both uplinks disable
> CONFIG_IP_ROUTE_MULTIPATH_CACHED and you will have random traffic 
> distribiution between both links.
> 
> More details : 
>           http://lists.openwall.net/netdev/2007/03/14/50
>           http://lists.openwall.net/netdev/2007/03/12/76
>           http://lists.quagga.net/pipermail/quagga-users/2007-May/008469.html
>

Oh. I see. Thanks. BTW: google doesn't show that links when looking for 
multipath on linux :-)

Random load sharing over multiple routes is not a good idea, or maybe is 
it? Am I guessing right that with enough amount of traffic and having 
two nexthops it will split 50%/50% ?


> BGP always have alternative paths in BGP RIB and mostly don't insert them
> as multipath route to FIB.
> 
> Of course there is path : http://lebon.org.ua/quagga.html that force 
> route to be inserted to kernel with multiple gateways - but realy this
> is some kind of dirty-hack.

I know that site, but I thought that those patches were obsoleted, 
because of --multipath option when compiling quagga.

> Check thread 'Linux and BGP multipath' on quagga-dev, and especially this mail:
> 
>            http://lists.quagga.net/pipermail/quagga-dev/2007-April/004700.html


I know that also :). BTW: until now I was quite pleased with linux 
networking which quality is amazing. But now, when I need loadbalancing 
I am disapointed, because it doesn't support things that with cisco 
hardware you take for granted. I miss mostly recursive routes.

Something like that

	ip route add 80.245.177.4/32 via 80.245.176.11
	ip route add 10.0.0.0/24 via 80.245.177.4

It would solve problems with multipath bgp and loadbalancing because I 
could add remove additional routes to 80.245.177.4 (or some other 
imaginary loopback) and it would work as expected.

I hope it will be added some day :)

Thank you for your help!


-- 
Michał Margula, alchemyx at uznam.net.pl, http://alchemyx.uznam.net.pl/
"W życiu piękne są tylko chwile" [Ryszard Riedel]