PPA.Lab - Cisco Discovery Protocol

GNS3

1. Topology

2. Configure basic settings

R1

R1#enable
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 loo

PC-1

C:\>ipconfig

Windows IP Configuration


Ethernet adapter Local Area Connection 7:

   Connection-specific DNS Suffix  . :
   Link-local IPv6 Address . . . . . : fe80::858e:7937:150f:df1e%29
   IPv4 Address. . . . . . . . . . . : 172.16.1.10
   Subnet Mask . . . . . . . . . . . : 255.255.0.0
   Default Gateway . . . . . . . . . : 172.16.1.1


C:\>

3. Display Filters on Wireshark

cdp

4. Sample .pcap file

5. Definition

  • Cisco Discovery Protocol (formerly known as CDP)

  • Layer 2, media-independent, and network-independent protocol

  • Runs on Cisco devices

  • Enables networking applications to learn about directly connected devices nearby

  • Some of the information that Cisco Discovery Protocol can learn includes:

    • Cisco IOS version running on Cisco devices

    • Hardware platform of devices

    • IP addresses of interfaces on devices

    • Locally connected devices advertising Cisco Discovery Protocol

    • Interfaces active on Cisco devices, including encapsulation type

    • Hostname

    • Duplex setting

    • VLAN Trunking Protocol (VTP) domain

    • Native VLAN

6. Benefits of Cisco Discovery Protocol

  • Allows systems using different network layer protocols to learn about one another.

  • Facilitates management of Cisco devices by discovering them and discovering how they are configured.

  • Assists with troubleshooting Type-Length-Value Fields (TLV) fields.

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