[nsp] Cisco 2500 Traffic Limit and high cpu utilization.

[Mehmet Ali Suzen]

Hi,
Thanks for the tips, indeed. I have already tried NetFlow before,
but when I enable cef, router begins to malfunction. I don't
know what is wrong? Are there any conflict with the other 
switching mechanisms or service? 
-Mehmet

On Sat, Mar 06, 2004 at 10:28:21AM -0600, Terry Baranski wrote:
> > Hi All,
> > I am wondering what is the traffic limit that a cisco 
> > 2500 series routers can handle? And why do we get 
> > quite often high cpu load and IP load?  How can I 
> > prevent this? I tried WRED queuing on the interfaces 
> > it helps a bit but not sufficient.
> 
> Depends on average packet size and what performance-reducing features
> are enabled.  Make sure CEF switching is enabled and working, first and
> foremost:
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_tech_not
> e09186a00801e1e46.shtml
> 
> The 2500s are rated at 4400 packets-per-second (using CEF) with 64 byte
> packets, which comes to around 2.2Mbps.  As packet size increases the
> achievable packets-per-second tends to decrease, but the maximum
> bandwidth one can push through a router tends to go up because the
> packets are bigger.  A fairly limited number of tests with other router
> models show bandwidth increasing by around 3-4x as packet size goes from
> 64 bytes to 1500 bytes (Ethernet traffic).  That would put a 2500 at
> around 6-8Mbps with 1500 byte packets, but note that this is simply an
> estimate based on the performance profiles of some other routers.
> Others here may have done tests on the 2500 series specifically that
> they can share.
> 
> Note also that these numbers are best case; i.e., CEF enabled, large
> packets, no performance-reducing features enabled, and so forth.
> Average packet size is usually much lower than 1500 bytes on real
> networks.  And anytime you enable a feature that increases the work the
> router has to do on each packet (e.g., ACLs, NAT, policy routing, etc),
> performance will often suffer.  
> 
> -Terry
>