【概述】
CDP是Cisco Discovery Protocol的縮寫， 它是由思科公司推出的一種私有的二層網(wǎng)絡(luò)協(xié)議，它能夠運行在大部分的思科設(shè)備上面。通過運行 CDP 協(xié)議，思科設(shè)備能夠在與它們直連的設(shè)備之間分享有關(guān)操作系統(tǒng)軟件版本，以及IP地址，硬件平臺等相關(guān)信息。
CDP是Cisco Discovery Protocol的縮寫， 它是由思科公司推出的一種私有的二層網(wǎng)絡(luò)協(xié)議，它能夠運行在大部分的思科設(shè)備上面。通過運行 CDP 協(xié)議，思科設(shè)備能夠在與它們直連的設(shè)備之間分享有關(guān)操作系統(tǒng)軟件版本，以及IP地址，硬件平臺等相關(guān)信息。
【用途】
從CDP的字面意思我們可以理解到， 這是一種設(shè)備發(fā)現(xiàn)協(xié)議。 類似的協(xié)議有HP的LLDP（Link Layer Discovery Protocol）還有華為/H3C的 NDP（鄰居發(fā)現(xiàn)協(xié)議）協(xié)議。 CDP是一個二層的網(wǎng)絡(luò)協(xié)議， 默認(rèn)每60 秒向01-00-0C-CC-CC-CC這個組播地址發(fā)送一次通告， 如果在180 秒內(nèi)未獲得先前鄰居設(shè)備的CDP通告，它將清除原來收到的 CDP信息。因為它不依賴任何的三層協(xié)議，透過 CDP 協(xié)議，可以幫助我們解決一些三層錯誤配置的故障，比如錯誤的三層地址等等。
從CDP的字面意思我們可以理解到， 這是一種設(shè)備發(fā)現(xiàn)協(xié)議。 類似的協(xié)議有HP的LLDP（Link Layer Discovery Protocol）還有華為/H3C的 NDP（鄰居發(fā)現(xiàn)協(xié)議）協(xié)議。 CDP是一個二層的網(wǎng)絡(luò)協(xié)議， 默認(rèn)每60 秒向01-00-0C-CC-CC-CC這個組播地址發(fā)送一次通告， 如果在180 秒內(nèi)未獲得先前鄰居設(shè)備的CDP通告，它將清除原來收到的 CDP信息。因為它不依賴任何的三層協(xié)議，透過 CDP 協(xié)議，可以幫助我們解決一些三層錯誤配置的故障，比如錯誤的三層地址等等。
用途一：SNMP協(xié)議通過CDP MIB發(fā)現(xiàn)網(wǎng)絡(luò)拓?fù)?
SNMP 中結(jié)合使用 CDP 管理信息基礎(chǔ) MIB，能使網(wǎng)絡(luò)管理應(yīng)用獲知被管理設(shè)備類型和相鄰設(shè)備的 SNMP 代理地址，并向這些設(shè)備發(fā)送 SNMP 查詢請求。Cisco 發(fā)現(xiàn)協(xié)議支持 CISCO-CDP-MIB。通過返回的響應(yīng)信息，網(wǎng)絡(luò)管理應(yīng)用發(fā)現(xiàn)支持 CDP協(xié)議的網(wǎng)絡(luò)設(shè)備，并依此生成發(fā)現(xiàn)的網(wǎng)絡(luò)拓?fù)洹?/div>
用途二：通過CDP協(xié)議發(fā)現(xiàn)相鄰端口 Duplex不匹配
從CDP Version 2開始， CDP支持傳送端口的Duplex， Native VLAN ID以及VTP Domain等新的 TLV 值。雙工不匹配是一種比較難發(fā)現(xiàn)的網(wǎng)絡(luò)錯誤，它并不會帶來網(wǎng)絡(luò)的中斷但是它會造成某些應(yīng)用性能的急劇下降。
從CDP Version 2開始， CDP支持傳送端口的Duplex， Native VLAN ID以及VTP Domain等新的 TLV 值。雙工不匹配是一種比較難發(fā)現(xiàn)的網(wǎng)絡(luò)錯誤，它并不會帶來網(wǎng)絡(luò)的中斷但是它會造成某些應(yīng)用性能的急劇下降。
如下例：
SW1--------SW2
在SW1上
SW1#sh int f0/1
FastEthernet0/1 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0013.1ac8.e581 (bia 0013.1ac8.e581)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
//忽略其他顯示部分
SW1#sh run int f0/1
Building configuration...
Current configuration : 118 bytes
SW1--------SW2
在SW1上
SW1#sh int f0/1
FastEthernet0/1 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0013.1ac8.e581 (bia 0013.1ac8.e581)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
//忽略其他顯示部分
SW1#sh run int f0/1
Building configuration...
Current configuration : 118 bytes
!
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
speed 100
duplex full
end
同時交換機有錯誤消息提示
01:04:25: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
FastEthernet0/1 (not half duplex), with SW2 FastEthernet0/1 (half duplex).
另外一臺交換機上
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
speed 100
duplex full
end
同時交換機有錯誤消息提示
01:04:25: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
FastEthernet0/1 (not half duplex), with SW2 FastEthernet0/1 (half duplex).
另外一臺交換機上
SW2#sh int f0/1
FastEthernet0/1 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0012.01e8.6101 (bia 0012.01e8.6101)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half-duplex, 100Mb/s, media type is 10/100BaseTX//忽略其他部分
SW2#sh run int f0/1
Building configuration...
Current configuration : 94 bytes
!
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
end
同時交換機上有如下錯誤提示
01:05:43: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
FastEthernet0/1 (not full duplex), with SW1 FastEthernet0/1 (full duplex).
FastEthernet0/1 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0012.01e8.6101 (bia 0012.01e8.6101)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half-duplex, 100Mb/s, media type is 10/100BaseTX//忽略其他部分
SW2#sh run int f0/1
Building configuration...
Current configuration : 94 bytes
!
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
end
同時交換機上有如下錯誤提示
01:05:43: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
FastEthernet0/1 (not full duplex), with SW1 FastEthernet0/1 (full duplex).
用途三：通過 CDP協(xié)議發(fā)現(xiàn)相鄰Trunk端口的 Native VLAN ID 不一致
Trunk端口的Native VLAN ID 不一致會導(dǎo)致部分VLAN 通訊出現(xiàn)混亂。
交換機 SW1通過F0/1 與SW2的 F0/2連接。
交換機 SW1通過F0/1 與SW2的 F0/2連接。
如下例：
交換機SW1上
SW1#
01:07:51: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered
on FastEthernet0/1 (22), with SW2 FastEthernet0/1 (1).
SW1#sh run int f0/1
Building configuration...
交換機SW1上
SW1#
01:07:51: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered
on FastEthernet0/1 (22), with SW2 FastEthernet0/1 (1).
SW1#sh run int f0/1
Building configuration...
Current configuration : 127 bytes
!
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport trunk native vlan 22
switchport mode trunk
end
SW1#show cdp entry *
-------------------------
Device ID: SW2
Entry address(es):
Platform: Cisco WS-C3550-24, Capabilities: Switch IGMP
Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/1
Holdtime : 148 sec
Version :
Cisco IOS Software, C3550 Software (C3550-IPSERVICESK9-M), Version 12.2(35)SE,
RELEASE SOFTWARE (fc2)
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Sun 03-Dec-06 14:34 by yenanh
advertisement version: 2
Protocol Hello: OUI=0x00000C, Protocol ID=0x0112; payload len=27,
value=00000000FFFFFFFF010221FF000000000000001201E86100FF0000
VTP Management Domain: 'xixi'
Native VLAN: 1 (Mismatch) //對端 Native VLAN ID是 1
Duplex: full
Management address(es):
W1#sh int f0/1 trunk
!
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport trunk native vlan 22
switchport mode trunk
end
SW1#show cdp entry *
-------------------------
Device ID: SW2
Entry address(es):
Platform: Cisco WS-C3550-24, Capabilities: Switch IGMP
Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/1
Holdtime : 148 sec
Version :
Cisco IOS Software, C3550 Software (C3550-IPSERVICESK9-M), Version 12.2(35)SE,
RELEASE SOFTWARE (fc2)
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Sun 03-Dec-06 14:34 by yenanh
advertisement version: 2
Protocol Hello: OUI=0x00000C, Protocol ID=0x0112; payload len=27,
value=00000000FFFFFFFF010221FF000000000000001201E86100FF0000
VTP Management Domain: 'xixi'
Native VLAN: 1 (Mismatch) //對端 Native VLAN ID是 1
Duplex: full
Management address(es):
W1#sh int f0/1 trunk
Port Mode Encapsulation Status Native vlan
Fa0/1 on 802.1q trunking 22
Fa0/1 on 802.1q trunking 22
Port Vlans allowed on trunk
Fa0/1 1-4094
Port Vlans allowed and active in management domain
Fa0/1 1,10,20-22,28,33-34,99-100,102,121,323
Port Vlans in spanning tree forwarding state and not pruned
Fa0/1 10,20-21,28,33-34,99-100,102,121,323
用途四：通過 CDP協(xié)議PoE 受電設(shè)備申請 PoE 電源分配
PoE 是Power Over Ethernet的縮寫，也就是我們常說的 Inline Power，為解決一些小型以太網(wǎng)設(shè)備需要單獨供電的而推出的一種集中化供電方式。 利用現(xiàn)有的5 類雙絞線為那些小型的設(shè)備如IP Phone，無線的AP提供電力供應(yīng)。
在PoE 供電系統(tǒng)中，我們把提供電力供應(yīng)的設(shè)備叫 PSE（Power Supply Equipment）接收電力供應(yīng)的叫PD（Powered Device） 。在思科設(shè)備中 PSE 往往是那些中心端點支持 PoE供電的交換機或者交換模塊。而PD 設(shè)備則是那些需要遠(yuǎn)程供電的 IP Phone，無線 AP等等。
對于 PSE 和 PD 設(shè)備都為思科的設(shè)備，思科允許它們之間通過 CDP 交換信息，以期讓PSE 設(shè)備獲得PD 設(shè)備的真實需要的電源供應(yīng)功率。
Fa0/1 1-4094
Port Vlans allowed and active in management domain
Fa0/1 1,10,20-22,28,33-34,99-100,102,121,323
Port Vlans in spanning tree forwarding state and not pruned
Fa0/1 10,20-21,28,33-34,99-100,102,121,323
用途四：通過 CDP協(xié)議PoE 受電設(shè)備申請 PoE 電源分配
PoE 是Power Over Ethernet的縮寫，也就是我們常說的 Inline Power，為解決一些小型以太網(wǎng)設(shè)備需要單獨供電的而推出的一種集中化供電方式。 利用現(xiàn)有的5 類雙絞線為那些小型的設(shè)備如IP Phone，無線的AP提供電力供應(yīng)。
在PoE 供電系統(tǒng)中，我們把提供電力供應(yīng)的設(shè)備叫 PSE（Power Supply Equipment）接收電力供應(yīng)的叫PD（Powered Device） 。在思科設(shè)備中 PSE 往往是那些中心端點支持 PoE供電的交換機或者交換模塊。而PD 設(shè)備則是那些需要遠(yuǎn)程供電的 IP Phone，無線 AP等等。
對于 PSE 和 PD 設(shè)備都為思科的設(shè)備，思科允許它們之間通過 CDP 交換信息，以期讓PSE 設(shè)備獲得PD 設(shè)備的真實需要的電源供應(yīng)功率。
用途五：協(xié)同ODR工作
ODR是On-Demand Routing的縮寫，直譯可以翻譯成“按需路由” ，我們可以把它看做是基于CDP協(xié)議的一種路由協(xié)議或者把它看做CDP協(xié)議的一種增強功能。在IOS 11.2及以后版本開始支持這個特性。 ODR適合用在那些Hub and Spoke型的網(wǎng)絡(luò)結(jié)構(gòu)中（Hub and Spoke的網(wǎng)絡(luò)拓?fù)浣Y(jié)果我們可以把它理解成一個中心點，多個分支的網(wǎng)絡(luò)拓?fù)洹＜蟹种В?。我們只需要在Hub中心路由器上啟用router odr，分支路由器會自動在它的CDP更新中添加有關(guān)它網(wǎng)絡(luò)的TLV信息。
在中心路由器R1 上
R1#config t
R1(config)#router odr //啟動ODR路由。
R1(config-router)#end
R1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
10.0.0.0/24 is subnetted, 2 subnets
o 10.0.2.0 [160/1] via 192.168.0.2, 00:00:23 //學(xué)習(xí)到的 odr路由
C 10.0.1.0 is directly connected, Loopback0
192.168.1.0/30 is subnetted, 1 subnets
C 192.168.1.0 is directly connected, Serial0/0
在分支路由器R2 上
R2#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ODR是On-Demand Routing的縮寫，直譯可以翻譯成“按需路由” ，我們可以把它看做是基于CDP協(xié)議的一種路由協(xié)議或者把它看做CDP協(xié)議的一種增強功能。在IOS 11.2及以后版本開始支持這個特性。 ODR適合用在那些Hub and Spoke型的網(wǎng)絡(luò)結(jié)構(gòu)中（Hub and Spoke的網(wǎng)絡(luò)拓?fù)浣Y(jié)果我們可以把它理解成一個中心點，多個分支的網(wǎng)絡(luò)拓?fù)洹＜蟹种В?。我們只需要在Hub中心路由器上啟用router odr，分支路由器會自動在它的CDP更新中添加有關(guān)它網(wǎng)絡(luò)的TLV信息。
在中心路由器R1 上
R1#config t
R1(config)#router odr //啟動ODR路由。
R1(config-router)#end
R1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
10.0.0.0/24 is subnetted, 2 subnets
o 10.0.2.0 [160/1] via 192.168.0.2, 00:00:23 //學(xué)習(xí)到的 odr路由
C 10.0.1.0 is directly connected, Loopback0
192.168.1.0/30 is subnetted, 1 subnets
C 192.168.1.0 is directly connected, Serial0/0
在分支路由器R2 上
R2#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is 192.168.1.1 to network 0.0.0.0
10.0.0.0/24 is subnetted, 1 subnets
C 10.0.2.0 is directly connected, Loopback0
192.168.0.0/30 is subnetted, 1 subnets
C 192.168.0.0 is directly connected, Serial0/0
o* 0.0.0.0/0 [160/1] via 192.168.1.1, 00:00:13 //學(xué)習(xí)到的缺省路由
o - ODR, P - periodic downloaded static route
Gateway of last resort is 192.168.1.1 to network 0.0.0.0
10.0.0.0/24 is subnetted, 1 subnets
C 10.0.2.0 is directly connected, Loopback0
192.168.0.0/30 is subnetted, 1 subnets
C 192.168.0.0 is directly connected, Serial0/0
o* 0.0.0.0/0 [160/1] via 192.168.1.1, 00:00:13 //學(xué)習(xí)到的缺省路由
【報文格式】
CDP協(xié)議是一個二層協(xié)議，它主要依賴某些二層協(xié)議作為它的承載層。
LLC/SNAP: OUI值0x00000C protocol ID 值 0x2000.
Cisco HDLC:Protocol ID 值為0x2000
PPP:Protocol ID 值為0x0207
CDP協(xié)議Decode例子如下：
CDP協(xié)議是一個二層協(xié)議，它主要依賴某些二層協(xié)議作為它的承載層。
LLC/SNAP: OUI值0x00000C protocol ID 值 0x2000.
Cisco HDLC:Protocol ID 值為0x2000
PPP:Protocol ID 值為0x0207
CDP協(xié)議Decode例子如下：
Frame 1 (386 bytes on wire, 386 bytes captured)
Arrival Time: Oct 27, 2005 17:51:50.282947000
Time delta from previous packet: 0.000000000 seconds
Time since reference or first frame: 0.000000000 seconds
Frame Number: 1
Packet Length: 386 bytes
Capture Length: 386 bytes
Protocols in frame: eth:llc:cdp:data
IEEE 802.3 Ethernet
Destination: CDP/VTP (01:00:0c:cc:cc:cc) //特殊的組播目的地址
Source: Cisco_12:34:56 (00:07:85:12:34:56)
Length: 372
Logical-Link Control
DSAP: SNAP (0xaa) //DSAP和 SSAP 為 0xaa 說明后面跟著的是 SNAP
IG Bit: Individual
SSAP: SNAP (0xaa)
CR Bit: Command
Control field: U, func=UI (0x03)
000. 00.. = Command: Unnumbered Information (0x00)
.... ..11 = Frame type: Unnumbered frame (0x03)
Organization Code: Cisco (0x00000c) //SNAP OUI Field值
PID: CDP (0x2000) //Protocol ID
Cisco Discovery Protocol
Version: 2 //版本
TTL: 180 seconds //TTL即為 Holdtime 計數(shù)器時間
Checksum: 0xc2c3
Arrival Time: Oct 27, 2005 17:51:50.282947000
Time delta from previous packet: 0.000000000 seconds
Time since reference or first frame: 0.000000000 seconds
Frame Number: 1
Packet Length: 386 bytes
Capture Length: 386 bytes
Protocols in frame: eth:llc:cdp:data
IEEE 802.3 Ethernet
Destination: CDP/VTP (01:00:0c:cc:cc:cc) //特殊的組播目的地址
Source: Cisco_12:34:56 (00:07:85:12:34:56)
Length: 372
Logical-Link Control
DSAP: SNAP (0xaa) //DSAP和 SSAP 為 0xaa 說明后面跟著的是 SNAP
IG Bit: Individual
SSAP: SNAP (0xaa)
CR Bit: Command
Control field: U, func=UI (0x03)
000. 00.. = Command: Unnumbered Information (0x00)
.... ..11 = Frame type: Unnumbered frame (0x03)
Organization Code: Cisco (0x00000c) //SNAP OUI Field值
PID: CDP (0x2000) //Protocol ID
Cisco Discovery Protocol
Version: 2 //版本
TTL: 180 seconds //TTL即為 Holdtime 計數(shù)器時間
Checksum: 0xc2c3
Device ID: LAN354802 //TLV值，設(shè)備 ID
Type: Device ID (0x0001)
Length: 13
Device ID: LAN354802
Addresses //TLV值，地址
Type: Addresses (0x0002)
Length: 17
Number of addresses: 1
IP address: 192.168.2.62
Protocol type: NLPID
Protocol length: 1
Protocol: IP
Address length: 4
IP address: 192.168.2.62
Port ID: FastEthernet0/7 //接口信息
Type: Device ID (0x0001)
Length: 13
Device ID: LAN354802
Addresses //TLV值，地址
Type: Addresses (0x0002)
Length: 17
Number of addresses: 1
IP address: 192.168.2.62
Protocol type: NLPID
Protocol length: 1
Protocol: IP
Address length: 4
IP address: 192.168.2.62
Port ID: FastEthernet0/7 //接口信息
Type: Port ID (0x0003)
Length: 19
Sent through Interface: FastEthernet0/7
Capabilities //支持的功能
Type: Capabilities (0x0004)
Length: 8
Capabilities: 0x0000000a
.... .... .... .... .... .... .... ...0 = Not a Router
.... .... .... .... .... .... .... ..1. = Is a Transparent Bridge
.... .... .... .... .... .... .... .0.. = Not a Source Route Bridge
.... .... .... .... .... .... .... 1... = Is a Switch
.... .... .... .... .... .... ...0 .... = Not a Host
.... .... .... .... .... .... ..0. .... = Not IGMP capable
.... .... .... .... .... .... .0.. .... = Not a Repeater
Software Version //軟件版本信息
Length: 19
Sent through Interface: FastEthernet0/7
Capabilities //支持的功能
Type: Capabilities (0x0004)
Length: 8
Capabilities: 0x0000000a
.... .... .... .... .... .... .... ...0 = Not a Router
.... .... .... .... .... .... .... ..1. = Is a Transparent Bridge
.... .... .... .... .... .... .... .0.. = Not a Source Route Bridge
.... .... .... .... .... .... .... 1... = Is a Switch
.... .... .... .... .... .... ...0 .... = Not a Host
.... .... .... .... .... .... ..0. .... = Not IGMP capable
.... .... .... .... .... .... .0.. .... = Not a Repeater
Software Version //軟件版本信息
Type: Software version (0x0005)
Length: 225
Software Version: Cisco Internetwork Operating System Software
IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version
12.0(5)WC8, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2003 by cisco Systems, Inc.
Compiled Thu 19-Jun-03 12:37 by antonino
Platform: cisco WS-C3548-XL //平臺信息
Type: Platform (0x0006)
Length: 21
Platform: cisco WS-C3548-XL
Protocol Hello: Cluster Management
Type: Protocol Hello (0x0008)
Length: 36
Length: 225
Software Version: Cisco Internetwork Operating System Software
IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version
12.0(5)WC8, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2003 by cisco Systems, Inc.
Compiled Thu 19-Jun-03 12:37 by antonino
Platform: cisco WS-C3548-XL //平臺信息
Type: Platform (0x0006)
Length: 21
Platform: cisco WS-C3548-XL
Protocol Hello: Cluster Management
Type: Protocol Hello (0x0008)
Length: 36
OUI: 0x00000C (Cisco)
Protocol ID: 0x0112 (Cluster Management)
Cluster Master IP: 0.0.0.0
UNKNOWN (IP?): 0xFFFFFFFF (255.255.255.255)
Version?: 0x01
Sub Version?: 0x01
Status?: 0x21
UNKNOWN: 0xFF
Cluster Commander MAC: 00:00:00:00:00:00
Switch's MAC: 00:07:85:12:34:56
UNKNOWN: 0xFF
Management VLAN: 100
VTP Management Domain: mynet //VTP管理域信息
Type: VTP Management Domain (0x0009)
Protocol ID: 0x0112 (Cluster Management)
Cluster Master IP: 0.0.0.0
UNKNOWN (IP?): 0xFFFFFFFF (255.255.255.255)
Version?: 0x01
Sub Version?: 0x01
Status?: 0x21
UNKNOWN: 0xFF
Cluster Commander MAC: 00:00:00:00:00:00
Switch's MAC: 00:07:85:12:34:56
UNKNOWN: 0xFF
Management VLAN: 100
VTP Management Domain: mynet //VTP管理域信息
Type: VTP Management Domain (0x0009)
Length: 10
VTP Management Domain: mynet
Native VLAN: 105 //NATIVE VLAN ID 信息
Type: Native VLAN (0x000a)
Length: 6
Native VLAN: 105
Duplex: Full
Type: Duplex (0x000b)
Length: 5
Duplex: Full
CDP協(xié)議報文格式
【配置管理】
CDP在思科設(shè)備上的配置管理非常簡單。
（1） 全局下關(guān)閉打開CDP功能
缺省情況下CDP功能是打開的。
全局配置命令 cdp run //全局啟用CDP
no cdp run //全局關(guān)閉CDP
配置范例：
R1#sh cdp //顯示CDP全局配置信息
Global CDP information:
Sending CDP packets every 60 seconds //缺省每 60 秒發(fā)送一次 CDP通告
Sending a holdtime value of 180 seconds //CDP通告保持時間為 180秒
Sending CDPv2 advertisements is enabled //發(fā)送 CDP version 2的通告
R1#config t //進全局配置模式
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#no cdp run //全局關(guān)閉CDP
R1(config)#exit
R1#
*Mar 1 00:07:45.351: %SYS-5-CONFIG_I: Configured from console by console
R1#sh cdp //這個時候我們再 show相關(guān) CDP信息就會提示 CDP已經(jīng)關(guān)閉
% CDP is not enabled
（2） 端口下關(guān)閉打開CDP功能
我們除了可以在全局狀態(tài)下打開關(guān)閉 CDP 功能，我們也可以根據(jù)情況配置每個端口的
CDP功能的打開關(guān)閉
配置命令：
接口配置模式下 cdp enable //打開接口的 CDP功能
no cdp enable //關(guān)閉接口的 CDP功能
配置范例：
R1#sh cdp interface s0/0 //查看接口的 CDP配置
Serial0/0 is up, line protocol is up //接口狀態(tài)
Encapsulation HDLC //接口封裝格式
Sending CDP packets every 60 seconds //每 60 秒發(fā)送一次 CDP通告
Holdtime is 180 seconds //CDP通告保持時間為 180秒
R1#config t //進全局配置模式
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#int s0/0 //進接口配置模式
R1(config-if)#no cdp enable //關(guān)閉接口 CDP功能
R1(config-if)#exit
R1(config)#exit
R1#
*Mar 1 00:19:23.443: %SYS-5-CONFIG_I: Configured from console by console
R1#sh cdp interface s0/0 //這個時候我們顯示CDP信息得到空白信息
R1#sh cdp //全局CDP功能還是打開的
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
（3） 調(diào)整CDP計時器配置
缺省情況下發(fā)送計時器為60秒，保持計時器為 180秒
配置命令
全局配置模式下
cdp timer xx //配置發(fā)送計數(shù)器時間為 xx 秒
cdp holdtime xx //配置保持計時器時間為xx 秒
需要說明的有兩點：
第一點：保持計時器時間必須大于發(fā)送計時器時間，建議為至少 2 倍發(fā)送計時器時
間。
第二點：保持計時器是本機發(fā)送出去的 CDP 通告所攜帶，通告接收設(shè)備，本 CDP
通告保持多長時間。而非針對本機收到的CDP通告。
配置范例：
R1#sh cdp //先查看一下當(dāng)前 CDP計時器配置
Global CDP information:
Sending CDP packets every 80 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
R1#config t //進全局配置模式
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#cdp timer ? //看看 cdp發(fā)送計時器的配置范圍
<5-254> Rate at which CDP packets are sent (in sec)
R1(config)#cdp timer 90 //配置 CDP發(fā)送計時器為 90 秒
R1(config)#cdp holdtime ? //查看 CDP保持計時器的配置范圍
<10-255> Length of time (in sec) that receiver must keep this packet
R1(config)#cdp holdtime 200 //配置 CDP保持計時器的時間為 200
R1(config)#exit
R1#
*Mar 1 00:37:43.059: %SYS-5-CONFIG_I: Configured from console by console
R1#sh cdp //通過show cdp，發(fā)現(xiàn)計時器配置已經(jīng)更改
Global CDP information:
Sending CDP packets every 90 seconds
Sending a holdtime value of 200 seconds
Sending CDPv2 advertisements is enabled
（4） 允許發(fā)送CDP version2 的通告
缺省情況下思科設(shè)備是允許發(fā)送 CDP version2 的通告。
我們可以通過 no cdp advertise-v2關(guān)閉 CDP version2 通告的發(fā)送。
配置范例：
R1#sh cdp //檢查 cdp全局配置
Global CDP information:
Sending CDP packets every 10 seconds
Sending a holdtime value of 30 seconds
Sending CDPv2 advertisements is enabled
R1#config t //進全局配置模式
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#no cdp advertise-v2 //關(guān)閉發(fā)送 CDP version通告功能
R1(config)#exit
R1#show cdp //檢查 CDP全局配置，已經(jīng)關(guān)閉
Global CDP information:
Sending CDP packets every 10 seconds
Sending a holdtime value of 30 seconds
Sending CDPv2 advertisements is not enabled
R1#debug cdp packets //打開 CDP報文 debug模式
CDP packet info debugging is on
R1# //發(fā)送 version1的 CDP 報文
*Mar 1 00:52:23.759: CDP-PA: version 1 packet sent out on Serial0/0
對端R2 上
R2#show cdp nei detail //查看 CDP鄰居詳細(xì)信息
-------------------------
Device ID: R1
Entry address(es):
Platform: Cisco 3640, Capabilities: Router Switch IGMP
Interface: Serial0/0, Port ID (outgoing port): Serial0/0
Holdtime : 26 sec
Version :
Cisco IOS Software, 3600 Software (C3640-IS-M), Version 12.4(10a), RELEASE
SOFTW
ARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 11-Oct-06 20:52 by prod_rel_team
advertisement version: 1
（5） CDP相關(guān)show命令
Show cdp //檢查CDP全局配置信息
Show cdp neighbor
使用范例：
R1#show cdp //檢查CDP全局配置信息
Global CDP information:
Sending CDP packets every 10 seconds //發(fā)送時間間隔
Sending a holdtime value of 30 seconds //保持時間間隔
Sending CDPv2 advertisements is not enabled //CDPv2的通告功能
R1#show cdp traffic //顯示 CDP Counters，包含發(fā)送接收到的 CDP報文數(shù)量
CDP counters :
Total packets output: 96, Input: 137 //總共接收發(fā)送多少 CDP報文
Hdr syntax: 0, Chksum error: 0, Encaps failed: 1 //錯誤數(shù)量
No memory: 0, Invalid packet: 0, Fragmented: 0 //錯誤數(shù)量
CDP version 1 advertisements output: 62, Input: 54 //CDPv1的報文數(shù)量
CDP version 2 advertisements output: 34, Input: 83 //CDPv2的報文數(shù)量
R1#clear cdp counters //CDP Counters清零
R1#sh cdp traffic //檢查 CDP Counters清零后的效果
No memory: 0, Invalid packet: 0, Fragmented: 0
CDP version 1 advertisements output: 0, Input: 1
CDP version 2 advertisements output: 0, Input: 1
R1#show cdp nei //顯示設(shè)備發(fā)現(xiàn)的鄰居情況
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
R2 Ser 0/0 21 R S I 3640 Ser 0/0
------------------------------------------------------------------------------------------------------
//Device ID 設(shè)備的主機名（Hostname）
//Local Intrfce :本地接口
//Holdtme:CDP通告信息保持多長時間，單位秒
//Capability: R代表是路由器，S支持交換功能，I支持 IGMP多播管理
//Platform:平臺信息
//Port ID:
R1#clear cdp table //清除發(fā)現(xiàn)的鄰居情況
R1#show cdp nei //檢查清除后的效果，所有的鄰居信息被清除
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#show cdp neighbors detail //顯示 CDP鄰居詳細(xì)信息
-------------------------
Device ID: R2
Entry address(es):
Platform: Cisco 3640, Capabilities: Router Switch IGMP
Interface: Serial0/0, Port ID (outgoing port): Serial0/0
Holdtime : 19 sec
睿博工作室 .www.netlord.com.cn
第(12)頁
Version :
Cisco IOS Software, 3600 Software (C3640-IS-M), Version 12.4(10a), RELEASE
SOFTW
ARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 11-Oct-06 20:52 by prod_rel_team
advertisement version: 2
R1#show cdp interface //顯示接口的 CDP配置信息
Serial0/0 is up, line protocol is up
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
Serial0/1 is up, line protocol is down
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
Serial0/2 is up, line protocol is down
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
Serial0/3 is up, line protocol is down
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
R1#sh cdp interface s0/0 //顯示某個具體接口的 CDP配置信息
Serial0/0 is up, line protocol is up
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
R1#show cdp entry ?
* all CDP neighbor entries
WORD Name of CDP neighbor entry
R1#show cdp entry R2 //顯示鄰居 R2 的鄰接信息，結(jié)果和 show cdp nei detail一致
-------------------------
Device ID: R2
Entry address(es):
Platform: Cisco 3640, Capabilities: Router Switch IGMP
Interface: Serial0/0, Port ID (outgoing port): Serial0/0
Holdtime : 17 sec
Version :
Cisco IOS Software, 3600 Software (C3640-IS-M), Version 12.4(10a), RELEASE
SOFTW
ARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 11-Oct-06 20:52 by prod_rel_team
advertisement version: 2
（6） CDP相關(guān)Debug命令
見下例：
R2#debug cdp ?
adjacency CDP neighbor info
events CDP events
ip CDP ip info
packets CDP packet-related information
R2#debug cdp packets //打開 debug CDP報文功能
CDP packet info debugging is on
R2#
*Mar 1 01:16:20.279: CDP-PA: version 2 packet sent out on Serial0/0
*Mar 1 01:16:20.283: CDP-PA: version 1 packet sent out on Serial0/0
*Mar 1 01:16:26.163: CDP-PA: Packet received from R1 on interface Serial0/0
*Mar 1 01:16:26.167: **Entry found in cache**
【補充說明】
（1） 常見的CDP錯誤日志信息
%CDP-4-DUPLEX_MISMATCH : duplex mismatch discovered on [chars] ([chars]), with
[chars] [chars] ([chars]).
解釋：CDP發(fā)現(xiàn)雙工配置不匹配。
建議：修改接口雙工配置，保證它們工作在相同的雙工狀態(tài)下。
%CDP-4-NATIVE_VLAN_MISMATCH : Native VLAN mismatch discovered on [chars]
([dec]), with [chars] [chars] ([dec]).
解釋： CDP發(fā)現(xiàn)某802.1Q Trunk端口 Native VLAN ID 不一致
建議： 將兩端Native VLAN ID 配置修改為一致
（2） CDP Version1和Vesion 2 的區(qū)別
CDP Version1 和 Version2的主要區(qū)別在于 Version2 支持更多 TLV，比如交換機之間的 VVTP Domain，Duplex，Native VLAN ID 等等。這樣極大的擴充了 CDP的功能。
VTP Management Domain: mynet
Native VLAN: 105 //NATIVE VLAN ID 信息
Type: Native VLAN (0x000a)
Length: 6
Native VLAN: 105
Duplex: Full
Type: Duplex (0x000b)
Length: 5
Duplex: Full
CDP協(xié)議報文格式
【配置管理】
CDP在思科設(shè)備上的配置管理非常簡單。
（1） 全局下關(guān)閉打開CDP功能
缺省情況下CDP功能是打開的。
全局配置命令 cdp run //全局啟用CDP
no cdp run //全局關(guān)閉CDP
配置范例：
R1#sh cdp //顯示CDP全局配置信息
Global CDP information:
Sending CDP packets every 60 seconds //缺省每 60 秒發(fā)送一次 CDP通告
Sending a holdtime value of 180 seconds //CDP通告保持時間為 180秒
Sending CDPv2 advertisements is enabled //發(fā)送 CDP version 2的通告
R1#config t //進全局配置模式
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#no cdp run //全局關(guān)閉CDP
R1(config)#exit
R1#
*Mar 1 00:07:45.351: %SYS-5-CONFIG_I: Configured from console by console
R1#sh cdp //這個時候我們再 show相關(guān) CDP信息就會提示 CDP已經(jīng)關(guān)閉
% CDP is not enabled
（2） 端口下關(guān)閉打開CDP功能
我們除了可以在全局狀態(tài)下打開關(guān)閉 CDP 功能，我們也可以根據(jù)情況配置每個端口的
CDP功能的打開關(guān)閉
配置命令：
接口配置模式下 cdp enable //打開接口的 CDP功能
no cdp enable //關(guān)閉接口的 CDP功能
配置范例：
R1#sh cdp interface s0/0 //查看接口的 CDP配置
Serial0/0 is up, line protocol is up //接口狀態(tài)
Encapsulation HDLC //接口封裝格式
Sending CDP packets every 60 seconds //每 60 秒發(fā)送一次 CDP通告
Holdtime is 180 seconds //CDP通告保持時間為 180秒
R1#config t //進全局配置模式
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#int s0/0 //進接口配置模式
R1(config-if)#no cdp enable //關(guān)閉接口 CDP功能
R1(config-if)#exit
R1(config)#exit
R1#
*Mar 1 00:19:23.443: %SYS-5-CONFIG_I: Configured from console by console
R1#sh cdp interface s0/0 //這個時候我們顯示CDP信息得到空白信息
R1#sh cdp //全局CDP功能還是打開的
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
（3） 調(diào)整CDP計時器配置
缺省情況下發(fā)送計時器為60秒，保持計時器為 180秒
配置命令
全局配置模式下
cdp timer xx //配置發(fā)送計數(shù)器時間為 xx 秒
cdp holdtime xx //配置保持計時器時間為xx 秒
需要說明的有兩點：
第一點：保持計時器時間必須大于發(fā)送計時器時間，建議為至少 2 倍發(fā)送計時器時
間。
第二點：保持計時器是本機發(fā)送出去的 CDP 通告所攜帶，通告接收設(shè)備，本 CDP
通告保持多長時間。而非針對本機收到的CDP通告。
配置范例：
R1#sh cdp //先查看一下當(dāng)前 CDP計時器配置
Global CDP information:
Sending CDP packets every 80 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
R1#config t //進全局配置模式
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#cdp timer ? //看看 cdp發(fā)送計時器的配置范圍
<5-254> Rate at which CDP packets are sent (in sec)
R1(config)#cdp timer 90 //配置 CDP發(fā)送計時器為 90 秒
R1(config)#cdp holdtime ? //查看 CDP保持計時器的配置范圍
<10-255> Length of time (in sec) that receiver must keep this packet
R1(config)#cdp holdtime 200 //配置 CDP保持計時器的時間為 200
R1(config)#exit
R1#
*Mar 1 00:37:43.059: %SYS-5-CONFIG_I: Configured from console by console
R1#sh cdp //通過show cdp，發(fā)現(xiàn)計時器配置已經(jīng)更改
Global CDP information:
Sending CDP packets every 90 seconds
Sending a holdtime value of 200 seconds
Sending CDPv2 advertisements is enabled
（4） 允許發(fā)送CDP version2 的通告
缺省情況下思科設(shè)備是允許發(fā)送 CDP version2 的通告。
我們可以通過 no cdp advertise-v2關(guān)閉 CDP version2 通告的發(fā)送。
配置范例：
R1#sh cdp //檢查 cdp全局配置
Global CDP information:
Sending CDP packets every 10 seconds
Sending a holdtime value of 30 seconds
Sending CDPv2 advertisements is enabled
R1#config t //進全局配置模式
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#no cdp advertise-v2 //關(guān)閉發(fā)送 CDP version通告功能
R1(config)#exit
R1#show cdp //檢查 CDP全局配置，已經(jīng)關(guān)閉
Global CDP information:
Sending CDP packets every 10 seconds
Sending a holdtime value of 30 seconds
Sending CDPv2 advertisements is not enabled
R1#debug cdp packets //打開 CDP報文 debug模式
CDP packet info debugging is on
R1# //發(fā)送 version1的 CDP 報文
*Mar 1 00:52:23.759: CDP-PA: version 1 packet sent out on Serial0/0
對端R2 上
R2#show cdp nei detail //查看 CDP鄰居詳細(xì)信息
-------------------------
Device ID: R1
Entry address(es):
Platform: Cisco 3640, Capabilities: Router Switch IGMP
Interface: Serial0/0, Port ID (outgoing port): Serial0/0
Holdtime : 26 sec
Version :
Cisco IOS Software, 3600 Software (C3640-IS-M), Version 12.4(10a), RELEASE
SOFTW
ARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 11-Oct-06 20:52 by prod_rel_team
advertisement version: 1
（5） CDP相關(guān)show命令
Show cdp //檢查CDP全局配置信息
Show cdp neighbor
使用范例：
R1#show cdp //檢查CDP全局配置信息
Global CDP information:
Sending CDP packets every 10 seconds //發(fā)送時間間隔
Sending a holdtime value of 30 seconds //保持時間間隔
Sending CDPv2 advertisements is not enabled //CDPv2的通告功能
R1#show cdp traffic //顯示 CDP Counters，包含發(fā)送接收到的 CDP報文數(shù)量
CDP counters :
Total packets output: 96, Input: 137 //總共接收發(fā)送多少 CDP報文
Hdr syntax: 0, Chksum error: 0, Encaps failed: 1 //錯誤數(shù)量
No memory: 0, Invalid packet: 0, Fragmented: 0 //錯誤數(shù)量
CDP version 1 advertisements output: 62, Input: 54 //CDPv1的報文數(shù)量
CDP version 2 advertisements output: 34, Input: 83 //CDPv2的報文數(shù)量
R1#clear cdp counters //CDP Counters清零
R1#sh cdp traffic //檢查 CDP Counters清零后的效果
No memory: 0, Invalid packet: 0, Fragmented: 0
CDP version 1 advertisements output: 0, Input: 1
CDP version 2 advertisements output: 0, Input: 1
R1#show cdp nei //顯示設(shè)備發(fā)現(xiàn)的鄰居情況
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
R2 Ser 0/0 21 R S I 3640 Ser 0/0
------------------------------------------------------------------------------------------------------
//Device ID 設(shè)備的主機名（Hostname）
//Local Intrfce :本地接口
//Holdtme:CDP通告信息保持多長時間，單位秒
//Capability: R代表是路由器，S支持交換功能，I支持 IGMP多播管理
//Platform:平臺信息
//Port ID:
R1#clear cdp table //清除發(fā)現(xiàn)的鄰居情況
R1#show cdp nei //檢查清除后的效果，所有的鄰居信息被清除
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#show cdp neighbors detail //顯示 CDP鄰居詳細(xì)信息
-------------------------
Device ID: R2
Entry address(es):
Platform: Cisco 3640, Capabilities: Router Switch IGMP
Interface: Serial0/0, Port ID (outgoing port): Serial0/0
Holdtime : 19 sec
睿博工作室 .www.netlord.com.cn
第(12)頁
Version :
Cisco IOS Software, 3600 Software (C3640-IS-M), Version 12.4(10a), RELEASE
SOFTW
ARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 11-Oct-06 20:52 by prod_rel_team
advertisement version: 2
R1#show cdp interface //顯示接口的 CDP配置信息
Serial0/0 is up, line protocol is up
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
Serial0/1 is up, line protocol is down
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
Serial0/2 is up, line protocol is down
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
Serial0/3 is up, line protocol is down
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
R1#sh cdp interface s0/0 //顯示某個具體接口的 CDP配置信息
Serial0/0 is up, line protocol is up
Encapsulation HDLC
Sending CDP packets every 10 seconds
Holdtime is 30 seconds
R1#show cdp entry ?
* all CDP neighbor entries
WORD Name of CDP neighbor entry
R1#show cdp entry R2 //顯示鄰居 R2 的鄰接信息，結(jié)果和 show cdp nei detail一致
-------------------------
Device ID: R2
Entry address(es):
Platform: Cisco 3640, Capabilities: Router Switch IGMP
Interface: Serial0/0, Port ID (outgoing port): Serial0/0
Holdtime : 17 sec
Version :
Cisco IOS Software, 3600 Software (C3640-IS-M), Version 12.4(10a), RELEASE
SOFTW
ARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 11-Oct-06 20:52 by prod_rel_team
advertisement version: 2
（6） CDP相關(guān)Debug命令
見下例：
R2#debug cdp ?
adjacency CDP neighbor info
events CDP events
ip CDP ip info
packets CDP packet-related information
R2#debug cdp packets //打開 debug CDP報文功能
CDP packet info debugging is on
R2#
*Mar 1 01:16:20.279: CDP-PA: version 2 packet sent out on Serial0/0
*Mar 1 01:16:20.283: CDP-PA: version 1 packet sent out on Serial0/0
*Mar 1 01:16:26.163: CDP-PA: Packet received from R1 on interface Serial0/0
*Mar 1 01:16:26.167: **Entry found in cache**
【補充說明】
（1） 常見的CDP錯誤日志信息
%CDP-4-DUPLEX_MISMATCH : duplex mismatch discovered on [chars] ([chars]), with
[chars] [chars] ([chars]).
解釋：CDP發(fā)現(xiàn)雙工配置不匹配。
建議：修改接口雙工配置，保證它們工作在相同的雙工狀態(tài)下。
%CDP-4-NATIVE_VLAN_MISMATCH : Native VLAN mismatch discovered on [chars]
([dec]), with [chars] [chars] ([dec]).
解釋： CDP發(fā)現(xiàn)某802.1Q Trunk端口 Native VLAN ID 不一致
建議： 將兩端Native VLAN ID 配置修改為一致
（2） CDP Version1和Vesion 2 的區(qū)別
CDP Version1 和 Version2的主要區(qū)別在于 Version2 支持更多 TLV，比如交換機之間的 VVTP Domain，Duplex，Native VLAN ID 等等。這樣極大的擴充了 CDP的功能。
