CCNA RSE Lab: 10.1.2.5 Lab – Configure CDP and LLDP

CCNA RSE Lab: 10.1.2.5 Lab – Configure CDP and LLDP

Topology

ccna-rse-lab-configure-cdp-lldp-1

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. 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.

Instructor Note: Refer to the Instructor Lab Manual for the procedures to initialize and reload devices.

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:

Gateway:

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.

How often are CDP packets sent?
CDP packets are sent out every 60 seconds.

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

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

How many interfaces are participating in the CDP advertisement? Which interfaces are up?
Five interfaces are participating in CDP. The interfaces S0/0/1 and G0/1 are up.

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

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

e. What can you learn about ISP and S3 from the outputs of the show cdp neighbors detail command?
The output displays the IOS version, device model, and the IP Address on S0/0/1 interface for ISP. On S3, the output shows information, such as the IOS version, VTP management domain, and native VLAN, duplex.

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.

g. Issue the show cdp neighbors detail command on Gateway. What additional information is available?
The output includes the IP address for SVI on S3 that was just configured.

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.

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.

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.

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

Which command(s) would you use to verify that CDP has been disabled?
show cdp, show cdp neighbors, show cdp neighbors detail, or show cdp interface

j. Enable CDP globally on Gateway. How many interfaces are CDP enabled? Which interfaces are CDP disabled?
Four interfaces are CDP enabled. The interface S0/0/1 is 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.

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.

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

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

Issue the show lldp neighbors command. Which devices are neighbors to Gateway?
Currently there are no neighbors.

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.

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.

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

What port is used on S3 to connect to the Gateway router?
Port Fa0/5 is used on S3 is connected to the Gi0/1 port on Gateway.

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

ccna-rse-lab-configure-cdp-lldp-2

Reflection

Within a network, on which interfaces should you not use discovery protocols? Explain.
Discovery protocols should not be used on interfaces that are facing the external networks because these protocols provide insights about the internal network. This information allows attackers to gain valuable information about the internal network and exploit the network.

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
(Fa0/0)
Fast Ethernet 0/1
(Fa0/1)
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. Rather than list all 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 might contain one. For example, for an ISDN BRI interface, the string in parenthesis is the legal abbreviation that can be used in Cisco IOS commands to represent the interface.

Device Configs – Final

Router ISP

Router Gateway

Switch S1

Switch S2

Switch S3

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