There are some SNMP OID's that you can use to monitor Netflow TCAM
utilization and Netflow learn failures. I don't have them handy, but if I
find them I'll post them.

We found that even during the summer break our TCAM tables where often full
and 1000's of flows per second were failing to be recorded. We are using
fairly aggressive timers, too. These are sup 720's with PFC 3BXL's and
DFC's. We are implementing optical taps on certain links to address these
issues.

If you are trying to collect flow data from sup720's on busy networks,
please keep in mind you may not be getting as complete a picture as you
think.

-Neil


-- 
Neil Johnson
Network Engineer
ITS-Telecommunications and Network Services
The University of Iowa
319 384-0938

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Shane
Gaumond
Sent: Wednesday, December 05, 2007 1:38 PM
To: [email protected]
Subject: [Nfsen-discuss] Netflow TCAM threshold exceeded

I run the following on my cat 6K
I have no problems..

IOS Version 12.2(18)
ip flow-cache timeout inactive 10
ip flow-cache timeout active 1
no ip flow export layer2-switched vlan 1-4094 mls netflow usage notify 80
120 mls flow ip interface-full no mls flow ipv6 ip flow-export version 9


The timeout values keep my graph less spikey "comb like"

I think the layer 2 flows are filling up your buffers and causing your
error.  Whenever i enable the layer 2 flows i get a whole lot of data.
most of it is useless ARP replys, OSPF, HSRP etc.  I think if you
disable the layer 2 reporting you should be fine. You can still enable
layer 2 for a few vlans if you really need that info but layer 2 data
for the whole chassis will overrun buffers. I also run Version 9 which
is supposed to be more efficient.   

I disagree with the netflow being automatic or broken on the Cat6k.  I
had to enable "ip flow ingress" on all my vlan interfaces to have the
chassis report flows for the interfaces.  Netflow reporting worked
exactly like Cisco said it would.

My only complaint of netflow on the Cat6K is that netflow will only
report IFindexes of interfaces with IP's.  This rules out switchports.
The ifindex reported in flows will always be the ifindex of the vlan
interface and never the physical interface.  Unless the physical
interface has an IP and "IP flow ingress" configured which is not
standard.    


Shane


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