Router High Utilization With Multilink PPP

chetann · ‎10-31-2003

Hi,

I have 3 2MB links bundeled in an Multilink PPP. Both the ends I have a 3640 router 32MB Flash & 64MB DRAM. When I FTP an 100MB file from one location to another, the router utilization shoots up to 90%. Has anyone experienced such a problem before.

Thanks in Advance

tbaranski · ‎10-31-2003

Is CEF enabled? If all the packets are being process-switched, that could be the issue.

chetann · ‎11-02-2003

Hi,

I have enabled CEF but it still dosent help.

Regards

Chetan

ruwhite · ‎11-03-2003

Could you post the output of the first few lines of show proc cpu? We need to know whether the high utilzation is in the interrupt path, or one of the processes.

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a00800a70f2.shtml

might be a good place to start.

Russ.W

chetann · ‎11-03-2003

Hi Russ,

The high utilization is on the interrupt path. But one question is, is it advisable to bundle 3 2MB links into a Multilink interface on a 3640 router, with majority of the traffic being RTP packets.

Thanks in Advance

Chetan

ruwhite · ‎11-04-2003

Okay, so check show alignment, and if that is clean, then I would say that the CPU on the bundling interfaces is where you're having issues. I would think that if this router isn't doing much else in terms of processing, such as routing protocols work, then you might be okay with 90% CPU utilization, to get the bundling. If you're uncomfortable with 90% CPU util (and I probably would be, but it would depend on where it is in the network), then I would think about trying to reduce the bundling in some way.

With three equal cost links, you could just run them as seperate paths, and let CEF do the load sharing between them. You probably won't get as close to equal sharing with CEF, but it would reduce your CPU utilization a good bit. And it would inject three parallel paths into the routing protocol.

Russ.W

chetann · ‎11-04-2003

Hi Russ,

Thanks a lot for the reply. I have disabled multilink & running each link as a separate path through static routes with CEF enabled. This has got down the utilization to 50%.

Thanks a Lot

Regards

Chetan