[LARTC] Load Balancing with 2 uplinks

[LARTC] Load Balancing with 2 uplinks

[Christoph Simon]

Hi,

I'm building a set of networks for a chain of cyber cafes. The
Internet connections are 512k ADSL links which work very
unreliably. There are at least a couple of hours each day they do not
work. Therefore the owner decided to put two of them in each network,
choosing a different ISP to minimize the probability that both fail at
the same time (which still happens). If one fails, we now can switch
manually to the other. Now, of course, I would like to use the right
interface for each connection, either the only one which is working,
or which is being less used. All client machines are routed through a
proxy server which also controls who may reach Internet at a given
time.

I have been looking for a solution to this problem for quite a while,
but most methods seem to be designed to address the inverse situation,
where one server can be reached by more than one links. Is there a way
to do this with the Linux 2.4?

Thanks in advance.

--
Christoph Simon
datageo@terra.com.br
---
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RE: [LARTC] Load Balancing with 2 uplinks

[Clemens Sibon]

Hi there,

> I have been looking for a solution to this problem for quite a while,
> but most methods seem to be designed to address the inverse situation,
> where one server can be reached by more than one links. Is there a way
> to do this with the Linux 2.4?

I have the same problem. I found a message about something similar on this
list (mail titled Re: [LARTC] Combining bandwith of two or more ADSLs ?,
dated april 10, 2001) but this didn't work for me:

I once had traffic over 2 interfaces (2 pings to different systems) but
after stopping and restarting the ping, they both took the same interface
out. I also noted traffic coming in on interface 1 and going out of
interface 2 (don't know why).

If I had sufficient hardware, I think that I would insert several extra PC's
with routing-software (www.zebra.org, since gated dumps core on me) and get
BGP or OSPF:

+--------+        +--------+
| adsl-1 |        | adsl-2 | 
+--------+        +--------+
     \                 /
      \               /
       \             /
        \           /
         \         /
          \       /
           \     /
         +--------+
         | proxy  |
         +--------+
              |
              |
              |
+-----------------------+
| Lot of other machines |
+-----------------------+

I did notice that when you have 2 BGP-routers both advertising a default
gateway, the system only uses 1. If this one fails, it starts using the
second but it won't switch back when the original comes back up again. I
have not yet played with OSPF but in theory, this should allow for some
load-balancing too.

Clemens Sibon
--
Pettemerstraat 12A                                  T r I p l e
1823 CW Alkmaar                                         T
Tel. +31 (0)72-5129516
fax. +31 (0)72-5129520                              Automatisering
www.triple-it.nl                                 "Laat uw Net Werken!"

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Re: [LARTC] Load Balancing with 2 uplinks

[Ramin Alidousti]

On Mon, May 21, 2001 at 03:36:50PM +0200, Clemens Sibon wrote:

> I did notice that when you have 2 BGP-routers both advertising a default
> gateway, the system only uses 1. If this one fails, it starts using the
> second but it won't switch back when the original comes back up again. I
> have not yet played with OSPF but in theory, this should allow for some
> load-balancing too.

If you assign a higher metric to the second one then when the first one
is available it will flush out the second one.

Ramin

> 
> Clemens Sibon
> --
> Pettemerstraat 12A                                  T r I p l e
> 1823 CW Alkmaar                                         T
> Tel. +31 (0)72-5129516
> fax. +31 (0)72-5129520                              Automatisering
> www.triple-it.nl                                 "Laat uw Net Werken!"
> 
> _______________________________________________
> LARTC mailing list / LARTC@mailman.ds9a.nl
> http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/

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Re: [LARTC] Load Balancing with 2 uplinks

[Christoph Simon]

On Mon, 21 May 2001 11:35:32 +0200 (MET DST)
Arthur van Leeuwen <arthurvl@sci.kun.nl> wrote:

> On Sun, 20 May 2001, Christoph Simon wrote:
> 
> > I have been looking for a solution to this problem for quite a while,
> > but most methods seem to be designed to address the inverse situation,
> > where one server can be reached by more than one links. Is there a way
> > to do this with the Linux 2.4?
> 
> Yes there is. Look at the posts I did in october and november of last year
> (sorry, don't have the URL's into the mailinglist archive handy). The
> problem will be automatic monitoring of whether or not your uplinks are
> indeed still up.

I did do this right now, but couldn't find a solution. That which came
closest, seems to have problems when one link is down (is this still
true with kernel 2.4.4?), which unfortunately is my case most of the
time. OTOH, I'm receiving lots of emails of other persons looking for
this solution. Would it be possible that some of those who worked on
that in october/november share their experiences in form of a
mini-howto? If not, I guess, a description of the basic strategy would
be very helpfull, as most of us don't even know where to start trying.

--
Christoph Simon
datageo@terra.com.br
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