Cisco Discovery Protocol （CDP）从名字我们就可以看出这是Cisco专有的了，建议大家学习CCNA的时候尽量熟悉全拼 不要简单的记下缩写！
CDP可以收集相邻的设备的硬件和协议信息
CDP有两个全局参数 ，可以进行设置
CDP timer(CDP定时器) 和 CDP holdtime（保持时间）
CDP定时器是多长时间将CDP数据包传输到所有接口的时间量。
CDP保持时间是设备保留从相邻设备接收到的数据包的时间量。
下面介绍下CDP的几个命令和区别
show cdp neighbors :作用是显示有关直连设备的信息，其中包括设备的主机名，接收数据包的端口或接口，保持时间，邻居设备的性能，设备类型和连接的端口ID
show cdp neighbors detail 显示的就比较详细了
和以上比较多了，直连设备的IP地址和IOS版本号。
show cdp entry * 与 show cdp neighbors detail 相同。
show cdp entry * protocols 显示直连邻居的IP地址。
show cdp entry * version 显示直连邻居的IOS版本。
show cdp traffic 显示了设备发送和接收的CDP数据包。
show cdp interface 显示每个接口使用的CDP信息，包括线路的封装类型，定时器和保持时间。
关闭CDP服务 no cdp run ,关闭某个接口的CDP 进入接口模式下 no cdp enable
当大家看完以上的命令的时候，想象一下，给你一个路由器 然后需要你根据CDP的
信息来配置IP和线缆的连接类型 以及设备类型 ，大家应该能做出来吧！下面我们来做以上实验
Router>en
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#host ccna1 设置路由器名
ccna1(config)#enable password cisco1 设置password
ccna1(config)#enable secret cisco2 设置secret
ccna1(config)#line vty 0 4
ccna1(config-line)#login
% Login disabled on line 66, until 'password' is set
% Login disabled on line 67, until 'password' is set
% Login disabled on line 68, until 'password' is set
% Login disabled on line 69, until 'password' is set
% Login disabled on line 70, until 'password' is set
ccna1(config-line)#pass cisco3 设置vty密码
ccna1(config-line)#exit
ccna1(config)#service password-encryption
ccna1(config)#int s
ccna1(config-if)#ip add 202.119.249.1 255.255.255.0 设置s0
ccna1(config-if)#clock rate 56000
ccna1(config-if)#no shut
%LINK-5-CHANGED: Interface Serial
ccna1(config-if)#exit
ccna1(config)#exit
%SYS-5-CONFIG_I: Configured from console by console
ccna1#
ccna2配置
Router>en
Router#Conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#host ccna2
ccna2(config)#enable password cisco1
ccna2(config)#enable secret cisco2
ccna2(config)#line vty 0 4
ccna2(config-line)#login
% Login disabled on line 66, until 'password' is set
% Login disabled on line 67, until 'password' is set
% Login disabled on line 68, until 'password' is set
% Login disabled on line 69, until 'password' is set
% Login disabled on line 70, until 'password' is set
ccna2(config-line)#password cisco3
ccna2(config-line)#exit
ccna2(config)#service password-encryption
ccna2(config)#int s
ccna2(config-if)#ip add 202.119.249.2 255.255.255.0
ccna2(config-if)#no shut
%LINK-5-CHANGED: Interface Serial
ccna2(config-if)#exit
ccna2(config)#int s1/1/1
ccna2(config-if)#ip add 202.119.248.1 255.255.255.0
ccna2(config-if)#clock rate 56000
ccna2(config-if)#no shut
%LINK-5-CHANGED: Interface Serial
ccna2(config-if)#end
%SYS-5-CONFIG_I: Configured from console by console
ccna3配置
Router>en
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#host ccna3
ccna3(config)#enable password cisco1
ccna3(config)#enable secret cisco2
ccna3(config)#line vty 0 4
ccna3(config-line)#login
% Login disabled on line 66, until 'password' is set
% Login disabled on line 67, until 'password' is set
% Login disabled on line 68, until 'password' is set
% Login disabled on line 69, until 'password' is set
% Login disabled on line 70, until 'password' is set
ccna3(config-line)#pass cisco3
ccna3(config-line)#exit
ccna3(config)#service password-encryption
ccna3(config)#int s
ccna3(config-if)#ip add 202.119.248.2 255.255.255.0
ccna3(config-if)#no shut
%LINK-5-CHANGED: Interface Serial
ccna3(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/1/0, changed state to upend
%SYS-5-CONFIG_I: Configured from console by console
ccna3#
主要内容ccna2上操作：
ccna2>en
Password:
ccna2#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
ccna1 Ser
ccna3 Ser 1/1/1 161 R C2800 Ser 1/1/0
ccna2#show cdp
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
ccna2#show cdp entry *
Device ID: ccna1
Entry address(es):
IP address : 202.119.249.1
Platform: cisco C2800, Capabilities: Router
Interface: Serial
Holdtime: 158
Version :
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 06:21 by pt_rel_team
advertisement version: 2
Duplex: full
---------------------------
Device ID: ccna3
Entry address(es):
IP address : 202.119.248.2
Platform: cisco C2800, Capabilities: Router
Interface: Serial
Holdtime: 152
Version :
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 06:21 by pt_rel_team
advertisement version: 2
Duplex: full
ccna2#show cdp entry ccna1
Device ID: ccna1
Entry address(es):
IP address : 202.119.249.1
Platform: cisco C2800, Capabilities: Router
Interface: Serial
Holdtime: 139
Version :
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 06:21 by pt_rel_team
advertisement version: 2
Duplex: full
---------------------------
ccna2#show cdp entry ccna3
Device ID: ccna3
Entry address(es):
IP address : 202.119.248.2
Platform: cisco C2800, Capabilities: Router
Interface: Serial
Holdtime: 129
Version :
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 06:21 by pt_rel_team
advertisement version: 2
Duplex: full
---------------------------
ccna2#show cdp entry ccna2
ccna2#un all
All possible debugging has been turned off
ccna2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
ccna2(config)#cdp run
ccna2(config)#exit
%SYS-5-CONFIG_I: Configured from console by console
ccna2#show cdp interfac
Vlan1 is administratively down, line protocol is down
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
FastEthernet0/0 is administratively down, line protocol is down
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
FastEthernet0/1 is administratively down, line protocol is down
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
Serial
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
Serial1/1/1 is up, line protocol is up
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
ccna2#debug ?
eigrp EIGRP Protocol information
frame-relay Frame Relay
ip IP information
搞定。。。。。
