Proper networking configuration in VMware ESXi is critical for performance, security, and manageability. This guide covers the essential settings every admin should know.

Understanding vSwitches

ESXi uses two types of virtual switches:

Standard vSwitch (vSwitch)

  • Managed per host
  • Simple configuration
  • Good for small environments

Distributed vSwitch (dvSwitch)

  • Managed at vCenter level
  • Centralized configuration
  • Better for larger deployments

Initial Configuration

1. Create Separate vSwitches

Segregate traffic types for security and performance:

vSwitch0: Management Network
vSwitch1: VM Traffic (Production)
vSwitch2: vMotion
vSwitch3: Storage (iSCSI/NFS)

2. Configure NIC Teaming

Set up NIC teaming for redundancy:

# Via ESXi CLI
esxcli network nic list
esxcli network vswitch standard uplink add --vswitch-name=vSwitch0 --uplink-name=vmnic1

Recommended teaming policies:

  • Route based on originating virtual port (default, good for most cases)
  • Route based on IP hash (requires EtherChannel on physical switch)
  • Route based on physical NIC load (best for load balancing)

3. Enable Jumbo Frames (for iSCSI/NFS)

If using iSCSI or NFS storage, enable jumbo frames end-to-end:

Physical Switch: MTU 9000
ESXi vmkernel port: MTU 9000
Storage array: MTU 9000

esxcli network vswitch standard set --vswitch-name=vSwitch3 --mtu=9000

Security Settings

1. Promiscuous Mode

Set to: Reject (default)

Prevents VMs from seeing all traffic on the vSwitch.

2. MAC Address Changes

Set to: Reject (default)

Prevents VMs from changing their MAC address.

3. Forged Transmits

Set to: Reject (default)

Prevents VMs from sending traffic with a different source MAC.

Exception: Nested Virtualization

If running nested ESXi or NSX-T, you may need to enable these on specific port groups:

Promiscuous Mode: Accept
MAC Address Changes: Accept
Forged Transmits: Accept

Performance Optimization

1. Use Multiple vmnics

Distribute traffic across multiple physical NICs:

Management: 2 x 1GbE (redundancy)
VM Traffic: 2 x 10GbE (performance)
vMotion: 2 x 10GbE (dedicated)
Storage: 2 x 25GbE (high throughput)

2. Enable Network I/O Control (NIOC)

Prioritize traffic types with NIOC:

Management: High shares
vMotion: Normal shares
VM Traffic: Normal shares
Storage: High shares (if shared)

3. Adjust TCP Offload Settings

For optimal performance, enable hardware offload:

esxcli network nic tso ipv4 set --nic-name=vmnic0 --enable=true
esxcli network nic tso ipv6 set --nic-name=vmnic0 --enable=true

Monitoring and Troubleshooting

Useful Commands

# List all vSwitches
esxcli network vswitch standard list

# Check NIC status
esxcli network nic list

# View vmkernel ports
esxcli network ip interface list

# Ping test with jumbo frames
vmkping -I vmk1 -s 8972 -d 192.168.10.10

Common Issues

Issue: Network Disconnectivity After vMotion

Cause: VLAN mismatch between hosts

Solution: Ensure all hosts have identical VLAN configurations

Issue: Slow Storage Performance

Cause: MTU mismatch or insufficient bandwidth

Solution: Verify jumbo frames end-to-end and check for bottlenecks

Conclusion

Proper ESXi networking configuration requires careful planning. Always:

  1. Segregate traffic types
  2. Implement redundancy with NIC teaming
  3. Secure your vSwitches
  4. Monitor performance regularly

Next up: Advanced dvSwitch configurations and NSX integration!