In this article, we go through CDP and also through LLDP, how to Enable Link Layer Discovery Protocol (LLDP) in vSwitch, but also for vDS and how to check the information in vCenter provided by this feature.

This week we install new ESXi hosts from a remote location. Since we did not have access physically to the Switches/ESXi hosts and we need to double-check if the cabling was correct, and also which interface was connected to which switch port.

When you have your vCenter and all VMware Infrastructure installed, this is easy to enable and discover. By using CDP (for CISCO) or Link Layer Discovery Protocol (LLDP for HP, Juniper, or others brands) Network teams can quickly get this information, even we can check this in the vCenter (see images below).

Since this was a new installation(new Switches, ESXi hosts, etc.), there was no vCenter and also no Storage Network (we still need to check where and which cables are connected). Since there was only one vSwitch created in the ESXi,  so I remember there was a way to configure this LLDP (we were using Juniper Switches) in the vSwitch using the vsish command.

Different ways to grab Physical Switches vs Virtual Switches information :

Listen mode – The ESXi/ESX host detects and displays information about the associated Cisco switch port, but information about the vSwitch is not available to the Cisco, Switch administrator.
Advertise mode – The ESXi/ESX host makes information about the vSwitch available to the Cisco switch administrator but does not detect and display information about the Cisco switch.
Both mode – The ESXi/ESX host detects and displays information about the associated Cisco switch and makes information about the vSwitch available to the Cisco, switch administrator.

Note: Depending on your Network / Virtual environment you can choose any of these options. In our implementations, most are set with Both, but some we use Listen. So check with your Network Teams what is the best option for them (or for Virtual Administrators).

How to configure CDP in Standard Switch (vSS):

For vSS we need to this by ESXi shell command.

First check what type of mode is set (listen is by default), then enable mode (add your mode option).

To enable LLDP in a vSwith is more complex.

Note: VMware doesn’t support LLDP in vSwitch, so please be careful using the next steps in Productions environments.

To enable this, we need to connect/read directly into the vSwitch with the command vsish.

Note: If you have more than one vSwitch already configured in your ESXi and want to enable LLDP in all vSwitch, you need to do the steps to all vSwitches(one at a time)

We use vSwitch0 to enable LLDP. Then we go to the folder for ports in this vSwitch0 and list all the ports that are available.

Again, connect to your host in the ESXi Shell.

So in this vSwitch0, we have all these ports

33554433/
33554434/
33554435/
33554436/
33554437/
33554438/

Then we need to check which port belongs to which vmnics (our ESXi Network Interfaces). To get the information from the vSwitch ports, we use get status for each port.

Just run the command to each port to identify which ones are from the vmnics.

Since this port doesn’t match a vmnic, let’s check the next one.

As we can see in the highlight, this port belongs to vmnic0. So do the same for all ports and then we enable the LLDP in the right ports.

In this case, these are the ports that were identified.

33554433 — management
33554434 — vmnic0
33554435 — shadow vmnic0
33554436 — vmnic9
33554437 — shadow vmnic9
33554438 — vmk0 (if you have any vmkernel in the vSwitch all are displayed here as a port)

So we need to enabled LLDP in port 33554434 and port 33554436. Because those are the physical ones, the rest is just virtual.

Enter the port folder and in the LLDP folder to enable LLDP.

Commands:

get enable – Provides the state of the LLDP (0 is disabled, 1 is enabled)
set enable 0/1 – is to enable or disable the LLDP

With these commands, you can enable LLDP in your ports.

I found a shell script in the https://gist.github.com/  that does the same trick for all vmnics in the vSwitch. Thanks to AnthonyWC for this script.

There are also some other script examples HERE.

Updated 24/04/2021: Grzegorz Kulikowski also wrote a nice LLDP PowerCLI script to do the same work. It worth trying if is easier for you, than using vsish.

Note: Did not test these scripts, so tested first in a test environment, before you used them in any production environment.

In vCenter:

After your vSwitches have all vmnics configured with LLDP, you can now check with Network Teams(or your own teams) the ports/interfaces connections.

Check in the next image where you can list the CDP / LLDP from the vSwitch using vSphere client (next section we can check how to see this through vSphere Web Client).

How to configure CDP/LLDP in vNetworking Distributed Switch (vDS):

Configuring CDP or LLDP in a vDS is much easier than in a vSS. Since we need vCenter o do this (vDS only works with vCenter ).

• Using vSphere Client:

1. Connect to vCenter Server using the vSphere Client.
2. On the vCenter Server home page, click Networking.
3. Right-click the vDS and click Edit Settings.
4. Select Advanced under Properties.
5. Using the checkbox and the dropdown, change the CDP settings.

• Using vSphere Web Client:

1. Connect to vCenter Server using the vSphere Web Client.
2. On the vCenter Server home page, click Networking.
3. Right-click the vDS and click Edit Settings.
4. Select Advanced under Properties.
5. Using the checkbox and the dropdown, change the CDP / LLDP settings.

Check in the next image where you can list the CDP / LLDP from the vSwitch using vSphere Web client.

The above tasks can be done in vSphere 5.x/6.7. Tasks and options are the same for every version.

Hope this information was useful.

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