Difference between "ip flow ingress" and "route-cache flow"?

[hoffa2000]

Greetings

Both ip flow ingress and route-cache flow commands are available on my Cat6513 IOS 12.2(18). When reading the the command reference it's unclear to me what the difference is.

Can someone please shed light on this for me?

Regards

Fredrik Hofgren

[mohammedmahmoud]

Hi,

The "ip route-cache flow" can be used only under the main interface, while the "ip flow ingress" was an enhancement to be used under subinterfaces.

The NetFlow Subinterface Support feature provides the ability to enable NetFlow on a per-subinterface basis. In a scenario in which your network contains thousands of subinterfaces and you want to collect export records from only a few subinterfaces, you can fine-tune your collection of data to only specified subinterfaces. The result is lower bandwidth requirements for NetFlow Data Export (NDE) and reduced platform requirements for NetFlow data-collection devices.

Using the NetFlow Subinterface Support feature, you can enable NetFlow on selected subinterfaces using the ip flow ingress command. If you configure the ip flow ingress command on a few selected subinterfaces and then configure the ip route-cache flow command on the main interface, enabling the main interface will overwrite the ip flow ingress command and data collection will start from the main interface as well as all the subinterfaces. In a scenario in which you configure the ip flow ingress command and then configure the ip route-cache flow command on the main interface, you can restore subinterface data collection by using the no ip route-cache flow command. This configuration will disable data collection from the main interface and restore data collection to the subinterfaces you originally configured with the ip flow ingress command.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080154dd2.html

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

[hoffa2000]

Thank you for clarifying the issue for me. As I understand, since I don't use subinterfaces, the effect of these two commands are the same.

[Hieu Cao]

Thanks for your great explanation. Good to know.

hieu

[royalblues]

Good explanation as always from Mohammed :-)

Narayan

[mohammedmahmoud]

Hi Narayan,

Thank you very much, i really appreciate to be appreciated from a person like your self :)

BR,

Mohammed Mahmoud.

[Essam Ahmad]

Al-salam alikom Mohammed,

What about this command:

ip route-cache same-interface

What's its purpose?

Thanks

[InayathUlla Sharieff]

Essam,

ip route-cache same-interface

“ip route-cache” controls the use of switching methods for forwarding IP packets:
ip route-cache [same-interface | flow | distributed | cef | policy]

• same-interface – Enables fast-switching packets to forward IP packets back out through the interface on which they arrived.

• flow – Enables NetFlow accounting for packets that are received by the interface.
• distributed – Enables distributed switching on the interface.
• cef – Enables Cisco Express Forwarding (CEF) operation on an interface.
• policy – Enables fast-switching for packets that are forwarded using Policy Based Routing (PBR).

HTH

Regards

Inayath

[Essam Ahmad]

Thanks Inayath,

I read this description before, but I couldn't understand what is it use for? when do we use it? and what are the benifits?

Best Regards,

[InayathUlla Sharieff]

Essam,
Regarding your query,  "ip route-cache same-interface"
will enable fast switching on the interface. It is not recommended as it
will put load on CPU but if your router has enough resources than you should
be alright.
 
You can verify what switching method is actually in use by issuing "sh ip
interface ."

By enabling fast-switching through this command , we are only enabling
fast-switching for same interface i.e. only for packets going out through
same interface on which they were received.


Normal cef switching will still be enabled.

HTH

Regards

Inayath

***Plz rate if this info is helpfull***********

[InayathUlla Sharieff]

Essam,

Did that clarified your doubt?