L2 Neighbor Discovery
- CDP (Cisco Discovery Protocol)
Default CDP Configuration
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Feature Default Setting
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CDP global state Enabled
CDP interface state Enabled
CDP timer (packet update frequency) 60 Seconds
CDP holdtimer (before discarding) 180 Seconds
CDP Version-2 advertisements Enabled
CDP Multicast destination address 01-00-0C-CC-CC-CC
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*Note: This MAC address also used for VTP,DTP,PAgP and UDLD
Link captured file Here
CDP Configuration
! Enable CDP Global
SW1(config)#cdp run
! Enable CDP per Interface
SW1(config)#in fas0/5
SW1(if-config)#cdp enable
! Check CDP Timers
SW1#show cdp
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
! Configure CDP Timers
SW1(config)#cdp timer 30 (Sec) Packet sent interval
! Configure Holdtime
SW1(config)#cdp holdtime 90 (Sec)
! Check CDP per Interface
SW1#show cdp interface fas 0/5
FastEthernet0/5 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 30 seconds
Holdtime is 90 seconds
! Check CDP Traffic
SW1#show cdp traffic
CDP counters :
Total packets output: 16, Input: 6
Hdr syntax: 0, Chksum error: 0, Encaps failed: 0
No memory: 0, Invalid packet: 0, Fragmented: 0
CDP version 1 advertisements output: 0, Input: 0
CDP version 2 advertisements output: 16, Input: 6
! Check CDP Neighbors
SW1#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
DSW1 Fas 0/24 133 S I WS-C3550-2Fas 0/24
SW1#show cdp neighbors detail
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Device ID: DSW1
Entry address(es):
IP address: 10.99.0.20
Platform: Cisco WS-C3550-24, Capabilities: Switch IGMP
Interface: FastEthernet0/24, Port ID (outgoing port): FastEthernet0/24
Holdtime : 157 sec
Version :
Cisco IOS Software, C3550 Software (C3550-IPSERVICESK9-M), Version 12.2(44)SE6, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Mon 09-Mar-09 20:28 by gereddy
advertisement version: 2
Protocol Hello: OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010221FF0000000000000013C4260B00FF0000
VTP Management Domain: 'CISCO'
Native VLAN: 99
Duplex: full
Management address(es):
IP address: 10.99.0.20
SW8#show cdp neighbors detail | include Device|address
Device ID: DSW1
Entry address(es):
IP address: 10.99.0.20
! Check only DSW1 entry
SW1#show cdp entry DSW1
