Examining Cisco Discovery Protocol (CDP) Output
Once you have Cisco Discovery Protocol (CDP) running and collecting data about your neighboring devices, you may want to view its output. This information about neighboring devices, is obtained by using the show cdp neighbors command.
The following is a list of options that go with that command. You can be specific about which neighbors you want to see, or you can show them all, and you can view summary data or detailed data.
Switch1>enable Switch1#show cdp neighbors ? Async Async interface BVI Bridge-Group Virtual Interface Dialer Dialer interface FastEthernet FastEthernet IEEE 802.3 Lex Lex interface Multilink Multilink-group interface Port-channel Ethernet Channel of interfaces Tunnel Tunnel interface Virtual-Template Virtual Template interface Virtual-TokenRing Virtual TokenRing Vlan Catalyst Vlans detail Show detailed information | Output modifiers <cr>
You can get detailed data with the cdp command. Here is detailed information that can be seen about my neighboring devices.
Notice the device type of RootBridge.edtetz.net; pick out which switch port can see Router2; and decode what IOS version is running on Switch2.
Switch1>enable Switch1#show cdp neighbors detail ------------------------- Device ID: Switch2 Entry address(es): IP address: 192.168.1.243 Platform: cisco WS-C2950-12, Capabilities: Trans-Bridge Switch Interface: FastEthernet0/12, Port ID (outgoing port): FastEthernet0/1 Holdtime : 137 sec Version : Cisco Internetwork Operating System Software IOS (tm) C2950 Software (C2950-C3H2S-M), Version 12.0(5.3)WC(1), MAINTENANCE INTERIM SOFTWARE Copyright (c) 1986-2001 by cisco Systems, Inc. Compiled Mon 30-Apr-01 07:56 by devgoyal advertisement version: 2 Protocol Hello: OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010121FF0000000000000006D6AC46C0FF0001 VTP Management Domain: '' Management address(es): ------------------------- Device ID: Router2 Entry address(es): IP address: 192.168.1.240 Platform: Cisco 2621XM, Capabilities: Switch IGMP Interface: FastEthernet0/3, Port ID (outgoing port): FastEthernet0/0 Holdtime : 142 sec Version : Cisco IOS Software, C2600 Software (C2600-ADVIPSERVICESK9-M), Version 12.3(4)T4, RELEASE SOFTWARE (fc2) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2004 by Cisco Systems, Inc. Compiled Thu 11-Mar-04 19:57 by eaarmas advertisement version: 2 VTP Management Domain: '' Duplex: full Management address(es): ------------------------- Device ID: RootBridge.edtetz.net Entry address(es): IP address: 192.168.1.103 Platform: AIR-AP350, Capabilities: Interface: FastEthernet0/1, Port ID (outgoing port): fec0 Holdtime : 131 sec Version : Cisco 350 Series AP 12.03T advertisement version: 2 Duplex: full Power drawn: 6.000 Watts Management address(es):
After reviewing the code, you should now know
RootBridge.edtetz.net is an AIR-AP350 — an Aironet 350 series access point
Router2 is seen by port FastEthernet0/3 — Router2 is using FastEthernet0/0
Switch2 is running IOS version 12.0
The show command offers a long list of items you can see information about. One of those items is cdp interface. The show cdp interface command provides you with detailed information about the interfaces CDP is running on. The output has been shortened to show only the first four switch interfaces. Notice that all the interfaces are still running at the default CDP configuration.
Switch1>enable Switch1#show cdp interface FastEthernet0/1 is up, line protocol is up Encapsulation ARPA Sending CDP packets every 60 seconds Holdtime is 180 seconds FastEthernet0/2 is up, line protocol is up Encapsulation ARPA Sending CDP packets every 60 seconds Holdtime is 180 seconds FastEthernet0/3 is up, line protocol is up Encapsulation ARPA Sending CDP packets every 60 seconds Holdtime is 180 seconds FastEthernet0/4 is down, line protocol is down Encapsulation ARPA Sending CDP packets every 60 seconds Holdtime is 180 seconds