vCenter Server Appliance MAC Address Mismatch Between VAMI and VM Network Adapter When Using DHCP Reservation

Products

• VMware vCenter Server

Issue/Introduction

• When using DHCP reservations for vCenter Server Appliance (VCSA) IP addressing, a discrepancy may be observed between the MAC address shown in the vCenter VM’s network adapter settings (VMX file or vSphere UI) and the MAC address displayed in the VCSA VAMI interface or via ifconfig.
  
  
• This behavior is commonly encountered when the vCenter Server was deployed with DHCP and later network adapter changes are performed at the VM level either during vCenter Upgrade or manually removing the Network Adapter for the VM and adding a new Network Adapter(vnic).
  
  
• The MAC address in VAMI and ifconfig output does not match the MAC address shown in:
• • vSphere Client → VM → Edit Settings → Network Adapter
  • VMX file configuration (ethernet0.generatedAddress)
    
    
• Recreating the network adapter or changing the MAC address at the VM level does not update the MAC address shown in VAMI or the guest OS.
  
  
• Removing the file /etc/systemd/network/00-eth0.link and rebooting while retaining DHCP causes loss of network connectivity.

Environment

VMware vCenter Server Appliance

Cause

This is expected behavior when the vCenter Server Appliance is deployed with DHCP.

During the initial deployment, the installer creates the file:

/etc/systemd/network/00-eth0.link

This file contains:

• Match section → Maps the interface to the VM MAC address.
  
  
• Link section → Binds the interface to the MAC address used during deployment.

As long as DHCP is used, the operating system continues to reference the original MAC address in this file, even if the VM network adapter MAC address changes later.

Resolution

Two approaches are available based on network configuration requirements:

Option 1: Continue Using DHCP Reservation (Recommended)

• Retain the existing MAC address from /etc/systemd/network/00-eth0.link.
  
  
• Use the MAC address displayed in VAMI(Appliance Management Interface for vCenter Server) for DHCP reservation to ensure consistent IP configuration across upgrades and reboots.
  
  
• No changes are required as this behavior is by design for DHCP deployments.

Option 2: Switch to Static IP Assignment

• Convert the vCenter Server network configuration from DHCP to static IP following: Configure the DNS, IP Address, and Proxy Settings
  
  
• Once static IP is configured, vCenter Server will start using the MAC address assigned to the VM’s network adapter in the vSphere environment.
  
  
• This approach is required if alignment between the VM network adapter MAC and the VCSA OS MAC is desired.

Important: Direct deletion of /etc/systemd/network/00-eth0.link while using DHCP is not supported and can result in network connectivity loss, requiring vCenter VM recovery from backup or snapshot.