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RE: is there a CDP log? [7:61471] posted 01/21/2003
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J. Johnson wrote:
> 
> Is there a CDP config option that will tell a cisco box to keep
> a log of CDP
> activity?  If so, how would an administrator access it?  It
> might be nice
> to see a history of when neighbors come up or go down, or when
> they change
> settings.
> 
> James
> 
> 

I found this to be pretty interesting:

____________________________
debug cdp
Use the debug cdp EXEC command to enable debugging of Cisco Discovery
Protocol (CDP). The no form of this command disables debugging output.

[no] debug cdp {packets | adjacency | events} 
Syntax Description

packets
 Enables packet-related debugging output.
 
adjacency
 Enables adjacency-related debugging output.
 
events
 Enables output related to error messages, such as detecting a bad checksum.
 


Usage Guidelines
Use debug cdp commands to display information about CDP packet activity,
activity between CDP neighbors, and various CDP events.

Sample Display
The following is sample output from debug cdp packets, debug cdp adjacency,
and debug cdp events commands:

Router# debug cdp packets
CDP packet info debugging is on
Router# debug cdp adjacency
CDP neighbor info debugging is on
Router# debug cdp events
CDP events debugging is on
CDP-PA: Packet sent out on Ethernet0
CDP-PA: Packet received from gray.cisco.com on interface Ethernet0
CDP-AD: Deleted table entry for violet.cisco.com, interface Ethernet0
CDP-AD: Interface Ethernet2 coming up
CDP-EV: Encapsulation on interface Serial2 failed
debug cdp ip
Use the debug cdp ip EXEC command to enable debug output for the IP routing
information that is carried and processed by the Cisco Discovery Protocol
(CDP). The no form of this command disables debugging output.


[no] debug cdp ip 
Usage Guidelines
CDP is a media- and protocol-independent device-discovery protocol that runs
on all Cisco routers.

You can use the debug cdp ip command to determine the IP network prefixes
CDP is advertising and whether CDP is correctly receiving this information
from neighboring routers.

Use the debug cdp ip command with the debug ip routing command to debug
problems that occur when on-demand routing (ODR) routes are not installed in
the routing table at a hub router. You can also use the debug cdp ip command
with the debug cdp packet and debug cdp adjacency commands along with
encapsulation-specific debug commands to debug problems that occur in the
receipt of CDP IP information.

Sample Display
The following is sample output from the debug cdp ip command. This example
shows the transmission of IP-specific information in a CDP update. In this
case, three network prefixes are being transmitted, each with a different
network mask.

Router# debug cdp ip
CDP-IP: Writing prefix 172.1.69.232.112/28
CDP-IP: Writing prefix 172.19.89.0/24
CDP-IP: Writing prefix 11.0.0.0/8
In addition to these messages, you might see the following messages:

This message indicates that CDP is attempting to install the prefix
172.1.1.0/24 into the IP routing table:
CDP-IP: Updating prefix 172.1.1.0/24 in routing table
This message indicates a protocol error occurred during an attempt to decode
an incoming CDP packet:
CDP-IP: IP TLV length (3) invalid
This message indicates the receipt of the IP prefix 172.1.1.0/24 from a CDP
neighbor connected via the Ethernet interface 0/0. The neighbor's IP address
is 10.0.01.
CDP-IP: Reading prefix 172.1.1.0/24 source 10.0.0.1 via Ethernet0/0
Related Commands
debug cdp adjacency
debug cdp packet
debug ip routing

________________________________

What the heck was all that stuff about exchanging prefixes via CDP?  



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