CEf adjacencies

Hello, What is the difference between Null, Discard and Drop adjacencies?
They seem to do the same.. Null0 is well known but the other 2?
 

Packets of This Adjacency Type
Receive This Processing

Null adjacency
Packets destined for a Null0 interface are dropped. Null adjacency can be
used as an effective form of access filtering.

Glean adjacency
When a router is connected to a multiaccess medium, the FIB table on the
router maintains a prefix for the subnet rather than for the individual host
prefixes. The subnet prefix points to a glean adjacency. A glean adjacency
entry indicates that a particular next hop should be directly connected, but
there is no MAC header rewrite information available. When the router needs
to forward packets to a specific host on a subnet, Cisco Express Forwarding
requests an ARP entry for the specific prefix, ARP sends the MAC address,
and the adjacency entry for the host is built.

Punt adjacency
The router forwards packets that require special handling or packets sent by
features that are not yet supported in conjunction with Cisco Express
Forwarding switching paths to the next higher switching level for handling.

Discard adjacency
The router discards the packets.

Drop adjacency
The router drops the packets.
 
 
http://www.cisco.com/en/US/partner/docs/ios/ipswitch/configuration/guide/cef
_overview_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1054829
 
 
Thanks Santiago E

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Received on Thu Jul 02 2009 - 11:23:26 ART