Re: [LARTC] LoadBalancing on many asimetric different dsl's.

[Alex Samad <alex@samad.com.au>]

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On Mon, Jan 22, 2007 at 10:03:21AM +0100, Jordi Segues wrote:
> Hello,
> 
> I've done this some montsh ago, with a command like:
> ip route add default equalize scope global nexthop  via $EXTGW1 dev
> $EXTIF1 weight 1 nexthop via $EXTGW2 dev $EXTIF2 weight 1
> 
> However, this is not the problem.
> While loadbalancing of simple requests worked fine, there where
> problems when you worked with connections. I mean HTTPS, of FTP
> connection for example.
> 
> The problem was fo me that the system trys to send packets of the same
> connection throught different gateways, so with different IP source
> (each DSL connection was from different ISP). This caused the server
> not to understand why the same connection sent packets with 2
> different source IP ;)
> Well, I hope you understand me.
> 
> If you would do real load balancing, and in a proper way, you should
> not only do it by link charge, but route packets by connection to.
> (routing all packets of the same connection through the same gateway)
> This is caused because you must flush the route cache some times (or
> packets to a destination will allways take the same route, wich is not
> a loadbalance).
> 
> So if someone has done it and doesn't have this problem, I'm interested too 
> :)

the above is actually covered in the wiki howto.  Bu tyou need to setup snat on
each interface, then connection tracking takes care of sending each stream out
the right interface, you need to use snat and not MASQ.

Then you need to setup up some ip rule tables for each of the interfaces.


my ip ru looks like this

0:      from all lookup local 
200:    from 144.132.145.38 lookup cable 
201:    from 60.241.248.86 lookup adsl 
32766:  from all lookup main 
32767:  from all lookup default 


my ip r sh tab default 

default  proto static  metric 5 
        nexthop via 144.132.144.1  dev vlan2 weight 1
        nexthop via 10.20.20.230  dev ppp0 weight 20
default via 10.20.20.230 dev ppp0  src 60.241.248.86  metric 20 
default via 144.132.144.1 dev vlan2  src 144.132.145.38  metric 30 


This works fine for me, I have tracked packets with tcpdump on both the server
and the client.

Alex



> 
> Thanks!
> 
> Jordi Segues
> 
> On 22 Jan 2007 09:49:28 +0100, sAwAr <sawar@interia.pl> wrote:
> >Hi,
> >
> >my company have just bought new network and I have question about one 
> >problem.
> >As in topic we must use few completely different dsl's and balance traffic 
> >between them.
> >2M/0,5M 4Mb/0,5M 8M/0,5M
> >M=Mb/s
> >I've never done such thing before so I have doubts how it will work. If 
> >the links are symmetric 2/2 4/4 8/8 there is no problem because with 
> >weights I can compensate  the difference between them and achieve nice 
> >results. But what in my situation?
> >My questions are: how to set load balancing to get all links equally 
> >loaded and avoid situation when the up load will be full and download 
> >almost empty? I believe this situation can happen due to fact that load 
> >balancing is based on flows and for example p2p or smpt/pop3 will eat 
> >whole upload.
> >If my problem isn't clear I'll try to explain it better later.
> >
> >
> >Thanks in advance.
> >Pozdrawiam
> >sawar
> >
> >----------------------------------------------------------------------
> >Wolne adresy pocztowe @interia.eu >>> http://link.interia.pl/f19e8
> >
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> 
> 
> -- 
> Jordi Segués Daina
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