Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Normal CPU performance for 2800

Hello,

is there any official Cisco reference to describe what is considered to be the highest acceptable production CPU load on 2800 routers?

I found the document "Integrated Services Routers G2 - Performance Overview" that states at page 5:

Most service providers set their CPU alarms to 60 or 65 percent. Many enterprise customers are comfortable running

production networks with CPU around 70 or 75 percent

I would like to find the same for G1. Any links, documents,...hints?

Thanks

Ivica

3 REPLIES
Super Bronze

Re: Normal CPU performance for 2800

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author has been advised of the possibility of such damage.

Posting

"Rules of thumb" for CPU don't really differ per device generation although "raw" performance does.  For example, for the same traffic you should see about the same CPU loading on a 3745 vs. a 2851, or on a 3825 vs. a 2911.

Software bases router performance is often very "sensitive" to the kind of traffic.  Traffic packet sizes and router configuration options can make huge differences to router CPU loading.  My experience has been many like even larger available CPU reserves to deal with the unexpected or growth.

I've attached a Cisco document that provides performance specs for routers prior to G2s.

New Member

Re: Normal CPU performance for 2800

Thanks for your document and answer, but I still need more formal reference to CPU load. The thing is I need to clearly demonstrate to my customer Cisco recommended production CPU load and the attached document does not talk about CPU loads (it deals with throughput of devices).

I am well aware that recommended load does not differ much from ISR G1 or G2 but the customer wants some hard evidence.

Thanks again

Ivica

Super Bronze

Re: Normal CPU performance for 2800

Disclaimer

The    Author of this posting offers the information contained within this    posting without consideration and with the reader's understanding that    there's no implied or expressed suitability or fitness for any  purpose.   Information provided is for informational purposes only and  should not   be construed as rendering professional advice of any kind.  Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In    no event shall Author be liable for any damages whatsoever  (including,   without limitation, damages for loss of use, data or  profit) arising  out  of the use or inability to use the posting's  information even if  Author has been advised of the possibility of such  damage.

Posting

Don't recall seeing such documentation.  Even the document you posted with its CPU recommendations is just a bit bogus.  Why bogus?  Well, as I've already noted CPU load can be highly variable based on traffic mix, and often traffic mix can change suddenly (both short term and long term).  Because of this, beyond saying we don't want a software based router to continuously hit 100% (because "bad" things happen when it does), it's extremely difficult to have a recommend CPU loading of one size fits all.  In some situation 20% might be too much and in others 80% might be just fine.  This situation is much like trying to provide a recommended link loading.  There too we might say less than 50% is good more than 50% isn't, but again, much depends on your traffic mix and network application requirements.

The only other recommendation you might go by is use queuing theory which describes expected "delays" as the average load increases.  Often queuing delay is very minimal below 50%.  Up to about 66% there's usually little delay.  Beyond about 66%, delays become common but they rapidly increase as you approach 100%.  Cisco's documented loadings of 60 to 75% fall in line with typical queuing theory.

569
Views
0
Helpful
3
Replies