[nsp] OSPF load balancing

[Stephen J. Wilcox]

On Thu, 14 Nov 2002, Ryan Roylance wrote:

> I have a design with 2 routers and two frame relay connections (1.5)
>      
> 
>          172.17.0.0/16       RA-----------a----------------RB
> 172.18.0.0/16
>                              RA-----------b----------------RB
> 
> I am running a single OSPF area utilizing the multiple path equal cost
> load balancing.  RA and RB are both Cisco 2621 routers.  
> 
> The question is this, by default the equal cost load balancing is per
> destination, so Im not getting a perfect balance,  I have a couple of
> servers on each side that see heavy traffic and they keep on ending up
> on the same link which defeats the purpose of having two lines.  When I
> switch to per packet load balancing the CPU on the routers goes way up
> (from 8% over 5 minutes to 25% over 5 minutes) and the performance drops
> ( I went from capping 1 at 1.5 to pushing 400 on each)  What solutions
> have people used in the past to make things like this happen?  Are the
> 2621's underpowered for what Im trying to do?   

thats the trouble with per packet .. what you actually do is turn off the
hardware switching and force it all onto the main CPU

the 2621s are fine, the trouble is the limitation of the routing protocols

my suggestion to you would be to manually influence the traffic, you can either
do this with a few static routes for the high volume servers or if you want to
complicate your config you could advertise more specifics for your servers and
then use an offset list to influence the ospf route to each specific

the simplest way is the static routes, in the event of a link failure you'll
still fall over to the alternate route but you will achieve the traffic
balancing you need..

Steve

> 
> thanks
> ryan 
> 
> Ryan Roylance
> Technical Operations Manager 
> OpSource
> 
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