Netflow on router 2921/K9

[phone.cam]

Hello,

Equipement: CISCO2921/K9

Cisco 22921 is used as Customer Edge

I have one interface g0/0 which is configured with subinterfaces (g0/0.200, g0/300). 

g0/0 haven't IP adress but each subinterface have IP address.

interface GigabitEthernet0/0
 no ip address
 no ip unreachables
 no ip proxy-arp
 duplex auto
 speed auto
 no mop enabled

interface GigabitEthernet0/0.200
 description 
 encapsulation dot1Q 200
 ip address 10.150.20.XX 255.255.255.248

Question : 

Is it possible to setup netflow just only on g0/0 to get all flow to this interface instead to setup on each subinterface?

[Verlein Ehouman]

Hello , 

Yes it is possible to configure Netflow just on the gig0/0.

By doing that you will only have one entry for both sub-interfaces  instead of having two separates entries.

[phone.cam]

Hello,

Thanks for your answer.

Can you tell me how to implement it  on 2921/K9?.

How can you do without IP adress on g0/0?.

regards.

[Verlein Ehouman]

Cisco recommend that Netflow should be configured on the physical interface as well as on the sub-interfaces.

The reason is that when configure only on sub-interfaces Netflow performs additional check for status of each sub-interfaces which requires more cpu processing.

But when enabled on the physical interface and sub-interfaces Netflow only check status of the physical interface so less cpu processing.

for more detail and configuration related command kindly refer to this link : 

http://www.cisco.com/c/en/us/td/docs/ios/12_2s/feature/guide/fs_nfsub.pdf

Regards 
Verlein

[Rima REL]

Hello Verlein,

I agree with you that cisco recommended that we can use Netflow on the physical interface as well as the subinterfaces. But they have never specified if we should have an IP adress on the Physical or not.

I read your link http://www.cisco.com/c/en/us/td/docs/ios/12_2s/feature/guide/fs_nfsub.pdf but I don't find the answer. 

As you know, in some configuration the physical adress is up but the ip adresses is unsinged. And till now I don't find a cisco documentation in which they specify with IP address or whitout it.

Regards,

Rim 

[Verlein Ehouman]

Hi Rim ,

The Netflow configuration doesn't require to have an ip on the physical interface.

As long as traffic flows through that interface , Netflow will be able to capture informations and create entries.

hope that answers your question.

Regards.
verlein

[Rima REL]

Yes thank you Verlein :)

Regards,

Rim

[phone.cam]

Hi verlein,

 is it depending on netflow version ? or any version  (5 and 9), implementation of netflow on physical interface on g0/0 is possible?.

[Verlein Ehouman]

hello ,

This is irrespective of the version you are using. Netflow version 9 is for MPLS

Regards
Verlein