ESXi hosts have intermittent or no network connectivity

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

The article outlines steps to verify network configuration and resolve any issues that may be causing a loss of connectivity.

 

Example:

• An ESXi host is experiencing intermittent connectivity issues.
• An ESXi host cannot connect to the network.

Notes:

• The steps in the article may need to be performed through remote console such as iLo, iDRAC, KVM, etc.
• If connection to the default gateway is successful, but connections to other subnets are unsuccessful, then there is an issue in routing/Layer 3. Contact your network team to determine why the Layer 3 connections are failing.

Environment

VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x

Resolution

Notes: 

• If a specific virtual machine is experiencing total network connectivity loss, see Troubleshooting virtual machine network connection issues.
• For information on how to test network connectivity to and from the ESXi host vmkernels, see Testing VMkernel network connectivity with the vmkping command.

Validate that each troubleshooting step below is true for your environment. The steps provide instructions or a link to a document for validating the process and taking any necessary remedial action. The steps are ordered in the most appropriate sequence to isolate the issue and identify the proper resolution. Please do not skip a step.

1. Verify that the network adapter and server hardware are supported. For more information, see Confirming ESX/ESXi host hardware (System, Storage, and I/O) compatibility
    
2. Verify that the network link is up. For more information, see Network adapter (vmnic) is down or fails with a failed criteria code.
    
3. Verify the physical network adapter has the latest driver/firmware. For more information, see Determining Network/Storage firmware and driver version in ESXi.
    
4. Verify that proper VLAN IDs exist on the portgroup. For more information, see VLAN configuration on virtual switches, physical switches, and virtual machines.
    
5. If you are using NIC teaming on the virtual switch, verify that the physical switch ports are configured consistently for each teamed network adapter and that the proper load balancing policy is configured on the virtual switch. VMware recommends you to use the default Route based on the originating virtual port ID load balancing policy. If port channel/ether channel on the physical switch is configured, use the Route based on IP hash load balancing policy on the virtual switch and if LACP is configured on the physical switch then it is recommended to use Route based on originating virtual port id on the distributed switch.(Note: It is not recommended to use IP hash when LACP is configured unless recommended by physical switch vendor). For more information, see NIC teaming in ESX/ESXi and Host requirements for link aggregation (etherchannel, port channel, or LACP) in ESXi.
    
6. Verify that the speed and duplex of the network links are consistent. VMware recommends having the physical adapters set to auto-negotiate. For more information, see Configuring the speed and duplex of an ESX/ESXi Server network adapter.
    
7. Verify that port security is not configured on the physical switch ports. For more information, see Loss of network connectivity when Cisco port security is configured on the physical switch.
    
8. Verify that portfast (or equivalent) is enabled on all of the ESXi host's physical switch ports. For more information, see STP may cause temporary loss of network connectivity when a failover or failback event occurs.
    
9. Verify that all the NICs participating as uplinks on the vSS and VDS are observing all the network information.  
   
   Note: Until the time the issue of observed IP range is not resolved on external physical network, you can set the problematic NIC in unused mode and then verify the networking functionality again.

If the problem still exists after trying the steps in this article, try to capture packets on the vmkernel , to see if packets are generated as expected and on the the physical NIC to determine if the traffic is sent to the physical environment. For more information, see Using the pktcap-uw tool in ESXi 5.5 and later.