[nsp] High CPU on 6400 NRP-1

[Dennis Peng]

Clayton Zekelman [clayton at mnsi.net] wrote:
> 
> 
> I'm having a strange problem on a 6400 NRP-1.
> 
> With 20 users terminating with PPPoE, and CEF on, the router runs at around 
> 75% CPU, most of it interrupt.  If I turn off CEF, it drops to around 1% 
> CPU.
> 
> I have another identical NRP that has around 450 users on it running at 22% 
> CPU with CEF on.
> 
> If I do a "show alignment" on the first unit with CEF on, the Spurious 
> Access counter climbs.  If I do it on the second unit, it does not.

Can you send me "show align" from the router with the high CPU?
Persistent alignment errors can easily cause the CPU to be much higher
then expected.

> Both are running 12.2(15)T1.  The configurations are roughly the same - the 
> only difference is the one with problems has a MTU of 1460 on the Virtual 
> Template, and the one without has an MTU of 1454.  I'm wondering if this is 
> causing the problem.  The users have been bounced a whole bunch lately, so 
> I'm not inclined to change it right now.
> 
> Interesting to note that I had a 7206 with an NPE-200 exhibiting the same 
> strange behavior, but when I swapped out to an NPE-225, it went away - CEF 
> worked fine.  From what I remember, the NRP-1 and the NPE-200 share some 
> architectural similarities.

That's true, although I'm still surprised that swapping to a NPE-225
made the problem go away.

Dennis

> I also have a couple of NRP-1's terminating around 900 users each through 
> L2TP running around 50% interrupt, with the Spurious Access counter 
> climbing.  Doesn't seem to be huge issue right now.
> 
> I'm wondering if the MTU issue and fragmentation are related to the high 
> interrupt load.  There is a bug ID (CSCeb87509) that talks about something 
> similar, but we're not running SSG, and its listed as un-reproduceable.
> 
> I can flip CEF on, and watch the router load go up, then switch it off, and 
> it goes right back down again.  I'm afraid that once I have more users on 
> the unit, I'll need CEF to be able to handle the load.
> 
> In all cases, I have dot1q trunking on the routers - this was listed in the 
> Bug ID as a condition.
> 
> Suggestions?  Insight?  Could it be fragging related to the MTU?
> 
> 
> 
> ---
> Clayton Zekelman
> Managed Network Systems Inc. (MNSi)
> 344-300 Tecumseh Rd. E.
> Windsor, Ontario
> N8X 5E8
> 
> tel. 519-985-8410
> fax. 519-258-3009 
> 
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