nanog mailing list archives

Re: Netflow on SUP720-3BXL


From: Andy Bierlair <globichen () gmail com>
Date: Sun, 15 Mar 2009 03:20:20 +0100

yes ip cef, this is enabled:

  IP fast switching is enabled
  IP fast switching on the same interface is disabled
  IP Flow switching is enabled
  IP CEF switching is enabled
  IP Flow switching turbo vector
  IP Flow CEF switching turbo vector

and so on...

-
Andy

On Sun, Mar 15, 2009 at 3:08 AM, Bill Blackford
<BBlackford () nwresd k12 or us> wrote:

just a shot in the dark. Do you have 'ip cef' in global config?

-b
________________________________________
From: Andy Bierlair [globichen () gmail com]
Sent: Saturday, March 14, 2009 6:55 PM
To: nanog () nanog org
Subject: Netflow on SUP720-3BXL

I’m trying to run netflow on one of our Cisco core routers (SUP720-3BXL),
but I think I am hitting some limitations because of this:



%EARL_NETFLOW-SP-4-TCAM_THRLD: Netflow TCAM threshold exceeded, TCAM
Utilization [99%]



The setup of netflow looks like this:



 ip flow-cache entries 524288

 mls aging fast time 5 threshold 32

 mls aging long 300

 mls aging normal 60

 mls netflow usage notify 80 300

 mls flow ip full

 no mls flow ipv6

 mls nde sender version 5

 no mls verify ip checksum

 no mls acl tcam share-global



 ip flow-export source Loopback0

 ip flow-export version 5 origin-as

 ip flow-export destination <ip> <port>



Then I have this enabled on all border interfaces/vlans (peering / transit /
other core routers) that are of interest for my stats:



 ip route-cache flow



Some more details about the problem:



#sh mls netflow table-contention detailed Earl in Module 5 Detailed Netflow
CAM (TCAM and ICAM) Utilization
================================================

TCAM Utilization             :   100%

ICAM Utilization             :   13%

Netflow TCAM count           :   262033

Netflow ICAM count           :   17

Netflow Creation Failures    :   4822220

Netflow CAM aliases          :   1





#sh mls netflow table-contention aggregate Earl in Module 5 Aggregate
Netflow CAM Contention Information
=============================================

Netflow Creation Failures    :   130003616

Netflow Hash Aliases         :   4





I understand that the TCAM is full, but what can I do against it? This is a
busy core router:



Aggregated traffic: 7-8 GBIT/s

Packets per Second: 1.0 - 1.2 Million



I wouldn't mind analyzing only every 10th or 100th flow, which seems to be a
common practice.



Any good piece of advice is welcome.



Thanks!



-
Andy


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