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Lab - Configure CDP and LLDP

Topology

Addressing Table

Device Interface IP Address Subnet Mask

Gateway

G0/1 192.168.1.254 255.255.255.0

S0/0/1 209.165.200.226 255.255.255.252

ISP S0/0/1 (DCE) 209.165.200.225 255.255.255.252

Objectives

Part 1: Build the Network and Configure Basic Device Settings

Part 2: Network Discovery with CDP

Part 3: Network Discovery with LLDP

Background / Scenario

Cisco Discovery Protocol (CDP) is a Cisco proprietary protocol for network discovery on the data link layer. It

can share information such as device names and IOS versions, with other physically connected Cisco

devices. Link Layer Discovery Protocol (LLDP) is vendor-neutral protocol using on the data link layer for

network discovery. It is mainly used with network devices in the local area network (LAN). The network

devices advertise information, such as their identities and capabilities to their neighbors.

In this lab, you must document the ports that are connected to other switches using CDP and LLDP. You will

document your findings in a network topology diagram. You will also enable or disable these discovery

protocols as necessary.

Note: The routers used with CCNA hands-on labs are Cisco 1941 Integrated Services Routers (ISRs) with

Cisco IOS Release 15.2(4)M3 (universalk9 image). The switches used are Cisco Catalyst 2960s with Cisco

IOS Release 15.0(2) (lanbasek9 image). Other routers, switches, and Cisco IOS versions can be used.

Lab – Configure CDP and LLDP

Depending on the model and Cisco IOS version, the commands available and the output produced might vary

from what is shown in the labs. Refer to the Router Interface Summary Table at the end of this lab for the

correct interface identifiers.

Note: Make sure that the routers and switches have been erased and have no startup configurations. If you

are unsure, contact your instructor.

Required Resources

• 1 Router (Cisco 1941 with Cisco IOS Release 15.2(4)M3 universal image or comparable)

• 3 Switches (Cisco 2960 with Cisco IOS Release 15.0(2) lanbasek9 image or comparable)

• Console cables to configure the Cisco IOS devices via the console ports

• Ethernet cables as shown in the topology

Part 1: Build the Network and Configure Basic Device Settings

In Part 1, you will set up the network topology and configure basic settings on the router and switches.

Step 1: Cable the network as shown in the topology.

The Ethernet ports used on the switches are not specified in the topology. You may choose to use any

Ethernet ports to cable the switches as shown in the topology diagram.

Step 2: Initialize and reload the network devices as necessary.

Step 3: Configure basic device settings for the switches.

a. Console into the device and enable privileged EXEC mode.

b. Enter configuration mode.

c. Disable DNS lookup to prevent the switch from attempting to translate incorrectly entered commands as

though they were host names.

d. Configure the hostname according to the topology.

e. Verify that the switchports with connected Ethernet cables are enabled.

f. Save the running configuration to the startup configuration file.

Step 4: Configure basic device settings for the routers.

a. Console into the device and enable privileged EXEC mode.

b. Enter configuration mode.

c. Copy and paste the following configurations into the routers.

ISP:

hostname ISP

no ip domain lookup

interface Serial0/0/1

ip address 209.165.200.225 255.255.255.252

no shutdown

Gateway:

hostname Gateway

Lab – Configure CDP and LLDP

no ip domain lookup

interface GigabitEthernet0/1

ip address 192.168.1.254 255.255.255.0

ip nat inside

no shutdown

interface Serial0/0/1

ip address 209.165.200.226 255.255.255.252

ip nat outside

no shutdown

ip nat inside source list 1 interface Serial0/0/1 overload

access-list 1 permit 192.168.1.0 0.0.0.255

d. Save the running configuration to the startup configuration file.

Part 2: Network Discovery with CDP

On Cisco devices, CDP is enabled by default. You will use CDP to discover the ports that are currently

connected.

a. On router Gateway, enter the show cdp command in the privileged EXEC mode to verify that CDP is

currently enabled on router Gateway.

Gateway# show cdp

Global CDP information:

Sending CDP packets every 60 seconds

Sending a holdtime value of 180 seconds

Sending CDPv2 advertisements is enabled

How often are CDP packets sent?

If CDP is disabled on Gateway, enable CDP by issuing the cdp run command in the global configuration

mode.

Gateway(config)# cdp run

Gateway(config)# end

b. Issue the show cdp interface to list the interfaces that are participating in CDP advertisements.

Gateway# show cdp interface

Embedded-Service-Engine0/0 is administratively down, line protocol is down

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

GigabitEthernet0/0 is administratively down, line protocol is down

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

GigabitEthernet0/1 is up, line protocol is up

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

Lab – Configure CDP and LLDP

Serial0/0/0 is administratively down, line protocol is down

Encapsulation HDLC

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

Serial0/0/1 is up, line protocol is up

Encapsulation HDLC

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

cdp enabled interfaces : 5

interfaces up : 2

interfaces down : 3

How many interfaces are participating in the CDP advertisement? Which interfaces are up?

c. Issue the show cdp neighbors command to determine the CDP neighbors.

Gateway# show cdp neighbors

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,

D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID

ISP Ser 0/0/1 158 R B S I CISCO1941 Ser 0/0/1

S3 Gig 0/1 170 S I WS-C2960- Fas 0/5

d. For more details on CDP neighbors, issue the show cdp neighbors detail command.

Gateway# show cdp neighbors detail

-------------------------

Device ID: ISP

Entry address(es):

IP address: 209.165.200.225

Platform: Cisco CISCO1941/K9, Capabilities: Router Source-Route-Bridge

Switch IGMP

Interface: Serial0/0/1, Port ID (outgoing port): Serial0/0/1

Holdtime : 143 sec

Version :

Cisco IOS Software, C1900 Software (C1900-UNIVERSALK9-M), Version 15.4(3)M2,

RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Compiled Fri 06-Feb-15 17:01 by prod_rel_team

advertisement version: 2

Management address(es):

IP address: 209.165.200.225

Lab – Configure CDP and LLDP

-------------------------

Device ID: S3

Entry address(es):

Platform: cisco WS-C2960-24TT-L, Capabilities: Switch IGMP

Interface: GigabitEthernet0/1, Port ID (outgoing port): FastEthernet0/5

Holdtime : 158 sec

Version :

Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 15.0(2)SE7,

RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Compiled Thu 23-Oct-14 14:49 by prod_rel_team

advertisement version: 2

Protocol Hello: OUI=0x00000C, Protocol ID=0x0112; payload len=27,

value=00000000FFFFFFFF010221FF0000000000000CD996E87400FF0000

VTP Management Domain: ''

Native VLAN: 1

Duplex: full

e. What can you learn about ISP and S3 from the outputs of the show cdp neighbors detail command?

f. Configure the SVI on S3. Use an available IP address in 192.168.1.0 / 24 network. Configure

192.168.1.254 as the default gateway.

S3(config)# interface vlan 1

S3(config-if)# ip address 192.168.1.3 255.255.255.0

S3(config-if)# no shutdown

S3(config-if)# exit

S3(config)# ip default-gateway 192.168.1.254

g. Issue the show cdp neighbors detail command on Gateway. What additional information is available?

h. For security reasons, it is a good idea to turn off CDP on an interface facing an external network. Issue

the no cdp enable in the interface configuration mode on the S0/0/1 interface on Gateway.

Gateway(config)# interface s0/0/1

Gateway(config-if)# no cdp enable

Gateway(config-if)# end

To verify that CDP has been turned off on the interface S0/0/1, issue the show cdp neighbors or show

cdp interface command. You may need to wait for the hold time to expire. The hold time is the amount of

time the network devices will hold the CDP packets until the devices discard them.

Gateway# show cdp neighbors

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,

Lab – Configure CDP and LLDP

D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID

S3 Gig 0/1 161 S I WS-C2960- Fas 0/5

The interface S0/0/1 on Gateway no longer has a CDP adjacency with the ISP router. But it still has CDP

adjacencies with other interfaces.

Gateway# show cdp interface

Embedded-Service-Engine0/0 is administratively down, line protocol is down

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

GigabitEthernet0/0 is administratively down, line protocol is down

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

GigabitEthernet0/1 is up, line protocol is up

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

Serial0/0/0 is administratively down, line protocol is down

Encapsulation HDLC

Sending CDP packets every 60 seconds

Holdtime is 180 seconds

cdp enabled interfaces : 4

interfaces up : 1

interfaces down : 3

i. To disable CDP globally, issue the no cdp run command in the global configuration mode.

Gateway# conf t

Gateway(config)# no cdp run

Gateway(config)# end

Which command(s) would you use to verify that CDP has been disabled?

j. Enable CDP globally on Gateway. How many interfaces are CDP enabled? Which interfaces are CDP

disabled?

k. Console into all the switches and use the CDP commands to determine the Ethernet ports that connected

to other devices. An example of the CDP commands for S3 is displayed below.

S3# show cdp neighbors

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,

D - Remote, C - CVTA, M - Two-port Mac Relay

Lab – Configure CDP and LLDP

Device ID Local Intrfce Holdtme Capability Platform Port ID

Gateway Fas 0/5 143 R B S I CISCO1941 Gig 0/1

S2 Fas 0/2 173 S I WS-C2960- Fas 0/4

S1 Fas 0/4 171 S I WS-C2960- Fas 0/4

Part 3: Network Discovery with LLDP

On Cisco devices, LLDP maybe enabled by default. You will use LLDP to discover the ports that are currently

connected.

a. On Gateway, enter the show lldp command in the privileged EXEC mode.

Gateway# show lldp

% LLDP is not enabled

If LLDP is disabled, enter the lldp run command in the global configuration mode.

Gateway(config)# lldp run

b. Use the show lldp command to verify that LLDP is enabled on Gateway.

Gateway# show lldp

Global LLDP Information:

Status: ACTIVE

LLDP advertisements are sent every 30 seconds

LLDP hold time advertised is 120 seconds

LLDP interface reinitialisation delay is 2 seconds

Issue the show lldp neighbors command. Which devices are neighbors to Gateway?

c. If there are no LLDP neighbors for Gateway, enable LLDP on the switches and ISP. Issue lldp run in the

global configuration mode on the devices.

S1(config)# lldp run

S2(config)# lldp run

S3(config)# lldp run

ISP(config)# lldp run

d. Issue the show lldp neighbors command on the switches and router to list the LLDP enabled ports. The

output for Gateway is shown below.

Gateway# show lldp neighbors

Capability codes:

(R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device

(W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID Local Intf Hold-time Capability Port ID

S3 Gi0/1 120 B Fa0/5

Total entries displayed: 1

e. Issue the show lldp neighbors detail command on Gateway.

Gateway# show lldp neighbors detail

Lab – Configure CDP and LLDP

------------------------------------------------

Local Intf: Gi0/1

Chassis id: 0cd9.96e8.7400

Port id: Fa0/5

Port Description: FastEthernet0/5

System Name: S3

System Description:

Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 15.0(2)SE7,

RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Compiled Thu 23-Oct-14 14:49 by prod_rel_team

Time remaining: 103 seconds

System Capabilities: B

Enabled Capabilities: B

Management Addresses:

IP: 192.168.1.3

Auto Negotiation - supported, enabled

Physical media capabilities:

100base-TX(FD)

100base-TX(HD)

10base-T(FD)

10base-T(HD)

Media Attachment Unit type: 16

Vlan ID: 1

Total entries displayed: 1

What port is used on S3 to connect to the Gateway router?

f. Use the show command outputs from CDP and LLDP to document the connected ports in the network

topology.

Lab – Configure CDP and LLDP

Reflection

Within a network, on which interfaces should you not use discovery protocols? Explain.

Router Interface Summary Table

Router Interface Summary

Router Model Ethernet Interface #1 Ethernet Interface #2 Serial Interface #1 Serial Interface #2

1800 Fast Ethernet 0/0

(F0/0)

Fast Ethernet 0/1

(F0/1)

Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)

1900 Gigabit Ethernet 0/0

(G0/0)

Gigabit Ethernet 0/1

(G0/1)

Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)

2801 Fast Ethernet 0/0

(F0/0)

Fast Ethernet 0/1

(F0/1)

Serial 0/1/0 (S0/1/0) Serial 0/1/1 (S0/1/1)

2811 Fast Ethernet 0/0

(F0/0)

Fast Ethernet 0/1

(F0/1)

Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)

2900 Gigabit Ethernet 0/0

(G0/0)

Gigabit Ethernet 0/1

(G0/1)

Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)

Note: To find out how the router is configured, look at the interfaces to identify the type of router and how many

interfaces the router has. There is no way to effectively list all the combinations of configurations for each router

class. This table includes identifiers for the possible combinations of Ethernet and Serial interfaces in the device.

The table does not include any other type of interface, even though a specific router may contain one. An

example of this might be an ISDN BRI interface. The string in parenthesis is the legal abbreviation that can be

used in Cisco IOS commands to represent the interface.

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