Answers: CDP/LLDP 1

certskills
By certskills May 31, 2016 09:10

 

CDP and LLDP configuration does not require a lot of thought, but it does help to practice them until the configuration is automatic. Also, if you do the configuration on any kind of gear or simulator, make sure to take the time to use the related show commands. Check out the lab requirements here.

Answers

Figure 1: Device Discovery Topology

Example 1: R1 Config

 

Example 2: R2 Config

 

Example 3: R3 Config

 

Example 4: R4 Config

 

Example 5: SW2 Config

 

Commentary

The default behavior of all Cisco devices is to have the Cisco Discovery Protocol (CDP) enabled on all interfaces. This behavior works well as long as the other deployed equipment in the network is either from Cisco or from a vendor that supports CDP. However, in cases where the connected device happens to use the standards-based Link Layer Discovery Protocol (LLDP), you need to disable CDP and enable LLDP.

For this lab you were tasked with a number of configuration tasks that test your ability to configure different configurations of CDP and LLDP; the specific order of the configuration is subjective.

On R1 and R2, the first task to configure is to enable LLDP globally with the lldp run global command. Then to run CDP only on some interfaces, and LLDP only on other interfaces, you need to use some interface subcommands. Specifically, to disable CDP on their G0/1 interfaces, use the no cdp enable interface subcommand. LLDP uses a slightly different command; to disable LLDP on the R1 and R2 G0/2 interfaces, use both the no lldp transmit and no lldp receive interface subcommands.

For R3 and R4, because both use LLDP only, you can disable CDP completely and then enable LLDP on all interface. First, to disable CDP globally, configure the no cdp run global command. Then, to enable LLDP globally, which automatically enables LLDP for both transmit and receive on all interfaces, configure the lldp run global command.

For the two switches, SW1 needs only default configuration, with CDP enabled globally and LLDP disabled globally, so no new configuration is needed. Example 11 shows the configuration to reverse those settings so that SW2 runs LLDP but not CDP.

CDP/LLDP 1
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certskills
By certskills May 31, 2016 09:10
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3 Comments

  1. Bakhodur March 6, 00:07

    Hello Mr. Wendell,
    Thanks a lot for this clarifying post!
    From your book: “To enable LLDP global, use the lldp run global command. Then, to enable it on each desired interface, you need to add two commands: lldp transmit and lldp receive.”
    From your post: “Then, to enable LLDP globally, which automatically enables LLDP for both transmit and receive on all interfaces, configure the lldp run global command.”
    The post is more clear than the book, because after reading your book I’ve thought that I need additionally to run lldp transmit and lldp receive on each desired interface.

    Reply to this comment
  2. Bav April 1, 11:13

    Hi Wendell,

    The LLDP configuration contradicts whats mentioned in this post. The book says that LLDP needs to be enabled globally and then you need to set the LLDP transmit and receive commands on each interface to enable LLDP on those interfaces.

    “Toenable LLDP global, use the lldp run global command. Then, to enable it on each desired
    interface, you need to add two commands: lldp transmit and lldp receive.”

    The post above suggests that enabling LLDP globally automatically results in LLDP being enabled on all interfaces.

    Which is correct please as both cannot be? Thanks

    Reply to this comment
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