Cisco Nexus 7000 netflow - missing data

[chunsingkerk]

Hi,

I've configured N7K to export layer 2 flows. Using 2 different flow collectors (open source and commercial), gaps/drops in the reported traffic are observed on a periodic basis.

Problem doesn't seems to be with the exporters, hence I wondering if netflow configuration on N7K can be tweaked to address this symptom.

Using the 'show exporter' command, no errors/drops are observed.

Here is my configuration:

======

flow record L2-Custom-Flow-Record

  match datalink mac source-address

  match datalink mac destination-address

  match datalink ethertype

  collect counter bytes

  collect counter packets

flow monitor TEST

  record L2-Custom-Flow-Record

  exporter FlOW-COLLECTOR

  exporter PLIXER

interface Ethernetx/y

...

  mac packet-classify

  layer2-switched flow monitor TEST input 

  no shutdown

====

switch: sh flow timeout

Flow timeout values

    Active timeout:           60 seconds

    Inactive timeout:         15 seconds

    Fast timeout:             Disabled

    Session aging timeout:    Disabled

    Aggressive aging timeout: Disabled

=====

I'm using NX-OS 5.0(5)

Anybody know what's wrong?

Kerk Chun Sing

[ameya_oke]

Hi Kerk,

After exactly 30 minutes the drop occurs, I believe some process triggers on Monitoring tool which is causing this.

Did you try plotting the graph on some other monitoring tool?

It need not be a Nexus issue.

Check for logs on Nexus and on monitoring tool as well.

Are you getting the same kind of trend with graphs for other devices?

Warm Regards

Ameya Oke

[chunsingkerk]

Hi Ameya,

Yes, I've exported and graph on 2 different monitoring tools. It is shown in the white (pmacct/cacti) and black (Plixer Scrutinizer) background graphs. The Plixer folks couldn't figure out what could be the problem as well.

Kerk Chun Sing

[sbhadrav@cisco.com]

I only have flexible netflow running on nx-os at L3 but looking at the doc theres a bit more required for L2 flows

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/system_management/configuration/guide/sm_nx_os_cg/sm_15netflow.html

Configuring Layer 2 NetFlow

You can define Layer 2 keys in flexible NetFlow records that you can use to capture flows in Layer 2 interfaces. The Layer 2 keys are as follows:

•Source and destination MAC addresses

•Source VLAN ID

•EtherType from the Ethernet frame

You can apply Layer 2 NetFlow to the following interfaces for the ingress direction:

•Switch ports in access mode

•Switch ports in trunk mode

•Layer 2 port channels.