RE: CEF EPOCH

Hi there,

Hahaha! the famous job interview question :)

If you are referring to the "epoch value" in CEF; it's 8 bits long (max 255)
and usually demonstrates "how many times your CEF table on that box has been
rebuild since the last reload". In fact for your FIB and adjacency tables it
plays the role of a global revision number. A little bit confusing but we also
have the same concept at "entry level"; for example when an entry gets added
to your table it gets your table's global Epoch number. So have the global
number; copy and paste on every new entry.

Any CCIE value?
NSF or the Graceful restart does need to update this number.

How is it used in NSF?
Well, after a switchover process you get new entries and they get a new Epoch
value (simply the global one). Don't worry about the old entries because they
get kicked out of the tables because they dont have the current "global" Epoch
value. You see this dependency between global and entry-level ones?

What if you hit 255?
It loops back to 0 and not 1!

Job interview question?
Increase the Epoch value to 13 ;) - Notepad heh?!

You may use the "clear ip cef epoch" to initiate the recreation process
manually.

This might help :
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.1E/native/co
mmand/reference/clear1.html#wp1039177

The Cisco press book is actuall y pretty cool on this but still a bit
confusing on how to use the global number.
--------------------------
Kambiz Agahian
CCIE (R&S)
CCSI, WAASSE, RSSSE
Technical Instructor
CCBOOTCAMP - Cisco Learning Solutions Partner (CLSP)
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-----Original Message-----
From: nobody_at_groupstudy.com on behalf of Bernard Steven
Sent: Mon 4/19/2010 11:55 PM
To: Cisco certification
Subject: CEF EPOCH

Experts ,

Some thing bugging my mind for some time.
What is Epoch ? All i know is it is a version control in the CEF table.
Also could not find a proper document.

Send a link if possible for details.

Blogs and organic groups at http://www.ccie.net
Received on Tue Apr 20 2010 - 00:40:06 ART