[j-nsp] "show ip cef exact-route"

Jesper Skriver jesper at skriver.dk
Tue May 15 03:14:33 EDT 2018

On Tue, May 15, 2018 at 02:32:07AM +0300, Saku Ytti wrote:
> Have you found cef exact-route to be correct?
> Last time I used this (ASR9000), it was giving wrong results to me. I
> think there is entirely separate piece of code for LAG result in
> software code and the CSCO EZChip microcode, and different people code
> IOS-XR than ezchip, so I think there is failure mode where one code is
> updated, and another is not, I hope I'm wrong.
> But if I'm right, then the only way to do this, is actually ask the
> microcode 'hey i have this packet, do a lookup for it', or like in
> CAT7600/ELAM, get lookup results for real traffic.

AFAIK it is broken on all hardware forwarding platforms from Cisco 
like Saku says, I added the hook in the IOS based ones for HW to
tell SW how it would hash a packet, but as I recall none of them
implemented it.

It is further complicated by the fact that different cards in the
same chassis may hash the same flow differently, so you'll get a
different answer depending on what linecard a packet came in on.


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