[nsp] Load Balancing

[Streiner, Justin]

On Wed, 15 Oct 2003, Bernardo Castilho Pinto wrote:

>   Which options exists to load sharing in two equal-cost links. My idea is to
> use two routers in my side and two routers in the ISP side. Can I do this using
> BGP + HSRP ? Is possilbe to do this without segmentation ?

HSRP doesn't really have any load-balancing mechanics built into it.

You mentioned BGP but didn't mention if you are multi-homed (have more
than one upstream provider).  If you are multi-homed and both of the links
you mentioned above go to the same provider and terminate on the same
router at both ends, you may  be able to use per-packet load-sharing using
CEF (if your provider supports it on their end) or multilink PPP to bond
the circuits together into a logical bundle.  If the two links go to
different providers, it's generally not possible to achieve a perfect
50/50 split in the traffic between them.  You may be able to tweak your
BGP settings to achieve a better traffic balance if necessary.

If you aren't multi-homed, BGP isn't needed.  In that case, CEF per-packet
load-sharing or multilink PPP would be better options.

Also, keep in mind differences in the round trip times of getting packets
across each circuit.  If you use a per-packet load-balancing method, you
can end up with packets in the same flow arriving at the destination out
of sequence.  Delay-sensitive applications like VOIP generally don't like
out-of-sequence packets.

jms