The Cisco Discovery Protocol (CDP) trusty looks ultimate enough, but there are quite a some info to undergo for success on the CCNA exam. In your CCNP studies, you'll be introduced to added uses for CDP, but for today it's sufficiency to undergo that CDP is fashioned to provide you aggregation regarding direct adjoining Cisco routers and switches.
CDP runs by choice between every direct adjoining Cisco devices. CDP is also a Cisco-proprietary prescript - if the direct adjoining figure is not a Cisco device, you won't wager the aggregation you wanted.
The base CDP bidding to pass aggregation most the direct adjoining edge is show cdp neighbor.
R2#show cdp neighbor
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
R1 BRI0 167 R 2521 Dialer1
This bidding is specially adjuvant when troubleshooting Cisco switches. Theres no requirement to analyse wiring in a demolition of Cisco devices to wager what routers are adjoining to a Cisco alter when exhibit cdp edge crapper be used. In the above output, you crapper wager the far device's hostname, what programme on the far figure is adjoining to the topical device, the aptitude of the far device, the far devices element platform, and the topical programme that is adjoining to the far device.
CDP crapper be unfit at both the orbicular and programme level. To alter CDP at the programme level, separate no cdp enable on the interface, and cdp enable to invoke it backwards on.
cdp official defines how ofttimes CDP packets are transmitted, and cdp holdtime defines how daylong a figure module stop a conventional packet.
To invoke CDP soured for the whole router, separate no cdp run. To analyse the underway orbicular position of CDP, separate exhibit cdp.
R2#show cdp
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime continuance of 180 seconds
CDP is streaming by default.
R2#conf t
R2(config)#cdp official 45
R2(config)#cdp holdtime 100
The CDP timers are changed.
R2#show cdp
Global CDP information:
Sending CDP packets every 45 seconds
Sending a holdtime continuance of 100 seconds
The CDP values hit been successfully changed. show cdp interface module provide the official aggregation for apiece programme on the router.
R2#conf t
R2(config)#interface bri0
R2(config-if)#no cdp enable
CDP is unfit on the BRI interface. This does NOT hit to be finished to ready the distinction from dialing.
R2#conf t
R2(config)#no cdp run
CDP is unfit globally.
R2#show cdp
% CDP is not enabled
CDP has been successfully disabled.
Show cdp edge gives you a enthusiastic care of information, but what if you requirement the neighbors IP address? Just separate exhibit cdp edge detail. You module intend modify more aggregation most that direct adjoining neighbor, including its IP address.
SW2#show cdp edge detail
-------------------------
Device ID: R4
Entry address(es):
IP address: 172.12.23.4
Platform: whitefish 2520, Capabilities: Router
Interface: FastEthernet0/4, Port ID (outgoing port): Ethernet0
Holdtime : 158 sec
The info of CDP are essential to you on the employ and in the CCNA communicating room. When you encounter yourself negotiating a seriously registered network, you crapper ingest CDP to walk finished the meshwork and create a meshwork transpose for your computer as well. Sometimes the simplest protocols are the most helpful!
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