[c-nsp] High CPU utilization on sup720 with GRE

[Simon Lockhart]

On Sun Mar 24, 2013 at 02:06:09PM +0300, Samir Abidali wrote:
> Can you somebody help me in understanding whey GRE tunnel Cisco
> WS-SUP720-3BXL , with two GRE tunnel configured will spike the cpur to 99%
> when the traffic goes beyond 30mbps.
> 
> According to documentation, the GRE is hardware accelerated, please note that
> the two tunnel interface has two different source interface ( SVI source ip
> address  )

It's important to use a different source interface for each Tunnel (we use
loopback interfaces per tunnel).

I'm doing over 1Gbps of GRE spread over multiple tunnels, and my CPU is running
at around 30%.

I'd probably start by looking at MTU - is this box having to do a lot of
fragmentation? That will kill the CPU very quickly.

Simon