What is Cisco Discovery Protocol – CDP? Explained with Examples

By | 9th November 2015

Cisco discovery protocol is a layer 2 protocol (OSI) that operates between Cisco devices such as Router and switches. CDP displays information about the directly connected devices such as device ID, Platform, connected interface, IOS versions, and layer 3 IP address.

We use the network topology below as an example

cdp

Topology Configuration

HQ#config t
HQ(config)#interface fa0/0
HQ(config-if)#ip address 172.16.1.1 255.255.255.0
HQ(config-if)#no shutdown

HQ(config-if)#interface fa0/1
HQ(config-if)#ip address 200.199.90.1 255.255.255.0
HQ(config-if)#no shutdown
HQ(config)#interface se0/0/0
HQ(config-if)#ip address 172.16.2.2 255.255.255.252
HQ(config-if)#no shutdown
HQ(config)#interface se0/0/1
HQ(config-if)#ip address 192.168.1.2 255.255.255.252
HQ(config-if)#no shutdown
HQ(config)#router eigrp 100
HQ(config-router)#network 172.16.1.0
HQ(config-router)#network 172.16.2.0
HQ(config-router)#network 200.199.90.0.
HQ(config-router)#network 192.168.1.0

HQ(config-router)#no auto-summary

BRANCH1

BRANCH1#config t

BRANCH1(config)#interface fa0/0

BRANCH1(config-if)#ip address 172.16.3.1 255.255.255.0

BRANCH1(config-if)#no shutdown

BRANCH1(config)#interface se0/0/0

BRANCH1(config-if)#ip address 172.16.2.1 255.255.255.252

BRANCH1(config-if)#no shutdown

BRANCH1(config)#interface se0/0/1

BRANCH1(config-if)#ip address 192.168.3.1 255.255.255.252

BRANCH1(config-if)#no shutdown

BRANCH1(config)#router eigrp 100

BRANCH1(config-router)#network 172.16.3.0

BRANCH1(config-router)#network 172.16.2.0

BRANCH1(config-router)#network 192.168.3.0

BRANCH1(config-router)#no auto-summary

BRANCH2

BRANCH2#config t

BRANCH2(config)#interface fa0/0

BRANCH2(config-if)#ip address 192.168.2.1 255.255.255.0

BRANCH2(config-if)#no shutdown

BRANCH2(config)#interface se0/0/0

BRANCH2(config-if)#ip address 192.168.1.1 255.255.255.252

BRANCH2(config-if)#no shutdown

BRANCH2(config)#interface se0/0/1

BRANCH2(config-if)#ip address 192.168.3.2 255.255.255.252

BRANCH2(config-if)#no shutdown

BRANCH2(config)#router eigrp 100

BRANCH2(config-router)#network 192.168.1.0

BRANCH2(config-router)#network 192.168.2.0

BRANCH2(config-router)#network 192.168.3.0

BRANCH2(config-router)#no auto-summary  

How to use show command to examine CDP configuration. The table below lists and explains the various CDP commands output.

cdp2

You can use Cisco Packet tracer for practice. Dont forget to configure clock rates on serial interfaces and a routing protocol (EIGRP)

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