Cisco Discovery Protocol

Sniffing and Evasion

Cisco Discovery Protocol (CDP) is a Layer 2, media-independent protocol developed by Cisco Systems. It enables Cisco devices to discover information about directly connected devices, facilitating efficient network management and troubleshooting.

Objectives:

• Understand the purpose and benefits of CDP.

• Learn how to configure basic settings on Cisco devices to utilize CDP.

• Use Wireshark to analyze CDP packets.

1. Network Topology:

The network setup for this tutorial includes a Cisco router (R1) connected to a PC (PC-1) via a FastEthernet interface.

Topology

2. Configuring Basic Settings:

On Router R1:

R1#configure terminal
R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address 172.16.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface loopback 0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R1(config-if)#^Z
R1#write memory
Warning: Attempting to overwrite an NVRAM configuration previously written
by a different version of the system image.
Overwrite the previous NVRAM configuration?[confirm]
Building configuration...
[OK]
R1#

On PC-1:

• Set IP Configuration:

PC> ip 172.16.1.100/24 172.16.1.1
Checking for duplicate address...
PC : 172.16.1.100 255.255.255.0 gateway 172.16.1.1

PC> show ip

NAME        : PC[1]
IP/MASK     : 172.16.1.100/24
GATEWAY     : 172.16.1.1
DNS         :
MAC         : 00:50:79:66:68:01
LPORT       : 20004
RHOST:PORT  : 127.0.0.1:20005
MTU         : 1500

PC> save
Saving startup configuration to startup.vpc
.  done

PC>

• Verify Configuration:

/R1#ping 172.16.1.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.1.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/8/16 ms
R1#

3. Analyzing CDP Packets with Wireshark:

• Install Wireshark:

  • Download and install Wireshark from the official website.

• Capture Traffic:

  • Launch Wireshark and start a capture on the interface connected to the network.

• Apply Display Filter:

  • Use the filter to display only CDP packets:

dcp

• Examine CDP Packets:

  • Observe details such as device ID, IP address, platform, and capabilities.

Keywords

CDP,Cisco Discovery Protocol,network topology,router configuration,Wireshark,packet analysis,IP addressing,troubleshooting,network management,FastEthernet,loopback interface,console access,SSH,network discovery,device identification,subnet mask,default gateway,Cisco devices,interface configuration,network monitoring, وایرشارک