The dillemma: You're accessing your server via SSH through interface eth1.102 with the ip 10.20.0.2/24 and gateway 10.20.0.1. Now you want to add eth1 to a linux bridge so you can hookin VMs on a vlan trunk.
Solution: Create a script which does everything in 1 go and call this script from screen. Make sure the script is flawless else you still loose your connection.
This is the script I create-bridge.sh used:
# First remove the old vlan device ip link set dev eth1.102 down ip link delete eth1.102 # Create the bridge brctl addbr br-eth1 brctl addif br-eth1 eth1 ip link set eth1 up ip link set br-eth1 up # Add the vlan tagging ontop of the bridge vconfig add br-eth1 102 ip link set br-eth1.102 up ip a add 166.111./24 dev br-eth1.102 ip route add default via 188.8.131.52
Now you should first open a screen session(maybe optional) and then call
./create-bridge.sh, which create your bridge and setup the previous interface ontop of the bridge without losing your SSH connection :)