RE: What is the difference between Punt Adjacency and Glean

Hi CCIE KID!

The punt adjacency of the Cisco Express Forwarding adjacency table occurs
when CEF does not possess the required information to switch the packet. CEF
uses this entry to trigger subsequent requests to use a "next best"
switching method such as Fast Switching in order to forward the packet. This
is easy for fans of American football to remember, as when a team no longer
believes they can move the ball forward, they PUNT and deliver the ball to
another team. I am proud to say my New England Patriots rarely ever punt
(except against the New York Jets in the playoffs).

A glean adjacency is what occurs when the device does not have ARP cache
address information for the destination. It will create the glean adjacency
in the table, and then go about the ARP process. This helps to avoid
ARP-based Denial of Service attacks for the local device. I remember this
one because I think of the device out on the network trying to "glean" the
information. According to Merriam-Webster, to glean is to "to gather
information or material bit by bit".

Note that these subtleties of Cisco Express Forwarding should be of most
concern during the CCIE written, as opposed to the CCIE lab exam.

I hope this post helps you!

Anthony Sequeira, CCIE, CCSI
StormWind's Epic Live

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of CCIE
KID
Sent: Friday, March 11, 2011 6:16 AM
To: Cisco certification
Subject: What is the difference between Punt Adjacency and Glean Adjancency

Can anyone tell me the difference between punt and glean adjacency?

-- 
With Warmest Regards,
CCIE KID
IN PURSUIT OF CCIE
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