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Just a quick post demonstrating how to failover the VMware management network to a second virtual switch. You probably want your “Management Network” traffic for your ESXi hosts to be separate from your VM traffic. Unfortunately, you don’t always have enough network capacity for two uplinks for each virtual switch. Below is a script that will effectively move the “Management Network” to a second vSwitch in instances where the uplink of the primary vSwitch becomes unavailable. Basically it provides software based failover of the Management Network by moving it to the virtual switch used for your VM traffic. Just place the script as a here doc in the /etc/rc.local file of ESXi and add a cron entry that runs it every 5 minutes or so. The script will also fail back to the original virtual switch once connectivity returns.

#!/bin/ash

vSwitch0_nic=$(esxcfg-vswitch -l | awk '$1 ~ /vSwitch0/ {print $6}')
ip=$(esxcfg-vmknic -l | awk '$2 ~ /Management/ && $3 ~ /Network/ {print $5}')
subnet=$(esxcfg-vmknic -l | awk '$2 ~ /Management/ && $3 ~ /Network/ {print $6}')

# vSwitch0 nic down
if ! esxcfg-nics -l | awk "$1 ~ /$vSwitch0_nic/ && $4 ~/Down/ {exit 1}"; then
    # "Management Network" on vSwitch0
    if esxcfg-vswitch -l | awk '/vSwitch0/,/Switch Name/' | grep -q 'Management Network'; then
        # remove "Management Network" from vSwitch0
        esxcfg-vmknic -d "Management Network"
        esxcfg-vswitch -D "Management Network" vSwitch0

        # add "Management Network" portgroup to vSwitch1 (vlan 96)
        esxcfg-vswitch -A "Management Network" vSwitch1
        esxcfg-vswitch --pg="Management Network" --vlan=96 vSwitch1

        # add "Management Network" VM Kernel NIC
        esxcfg-vmknic -a -i $ip -n $subnet "Management Network"
    fi
else
    # "Management Network" on vSwitch1
    if esxcfg-vswitch -l | awk '/vSwitch1/,/Switch Name/' | grep -q 'Management Network'; then
        # remove "Management Network" from vSwitch1
        esxcfg-vmknic -d "Management Network"
        esxcfg-vswitch -D "Management Network" vSwitch1

        # add "Management Network" portgroup to vSwitch0
        esxcfg-vswitch -A "Management Network" vSwitch0
        esxcfg-vswitch --pg="Management Network" vSwitch0

        # add "Management Network" VM Kernel NIC
        esxcfg-vmknic -a -i $ip -n $subnet "Management Network"
    fi
fi
[/bash]