How to check physical switch details over command line

Identifying Physical Switch Connectivity in vCenter Using lldpnetmap

When managing ESXi hosts in vCenter, one common challenge is visibility into the physical switch connections. While vCenter provides detailed information about virtual networking, it doesn’t always expose which physical switches the host NICs are connected to. This can make troubleshooting and auditing network paths more difficult.

The ChallengevCenter shows NICs and port groups but not the upstream switch details.

• Network admins often need to confirm which physical switch and port a NIC is connected to.

• This is especially important in environments with multiple switches, VLANs, or redundant uplinks.

The Solution: Use lldpnetmap

ESXi supports LLDP (Link Layer Discovery Protocol), which allows NICs to exchange information with connected switches. By logging into the ESXi host directly, you can query this data.

Login to ESXi Host

Access the ESXi host directly using SSH or a Putty session.

Open Putty → Enter ESXi host IP → Authenticate with root credentials

• Ensure SSH is enabled on the host

• Use secure credentials

Run the LLDP Command

Key Command

Execute the built-in command to fetch NIC-to-switch mapping.

lldpnetmap

• Displays all NICs on the host

• Shows connected switch names and port IDs

• Useful for verifying uplink connectivity

Interpret the Output

Review the displayed NIC and switch details to confirm connectivity.

• Each NIC will list the connected switch

• Port IDs help identify exact switch ports

• Cross-check with switch configuration for accuracy

Apply in Troubleshooting

Use the mapping to resolve network issues or validate configurations.

• Identify misconnected NICs

• Verify redundancy across switches

• Document physical connectivity for audits

Example Output

bash

# lldpnetmap
vmnic0 -> Switch01 Port Gi1/0/24
vmnic1 -> Switch02 Port Gi1/0/12

This output clearly shows which NIC is connected to which physical switch and port.

Benefits

• Faster troubleshooting: Quickly identify miswired or disconnected NICs.

• Improved documentation: Maintain accurate records of host-to-switch connectivity.

• Enhanced reliability: Validate redundancy and load balancing across multiple switches.