Replacing MX100 with MX105 that are currently in HA

[Stumps]

We are currently running two MX100's in HA and I we want to replace them with two MX105's and put them in HA for our network.  I know that we can not put one of the MX105's in as the space as it does not match the MX100 that is the primary.  What is the best way to do this?  Do I have to remove both from the network and then add in the mx105's or do I need to setup a new network and if so can I copy over the current configuration to the new network as we want the same settings on the mx105 as the mx100

[GIdenJoe]

If you have a combined network temporarily split it up.
Then make a new network which is a clone of the resulted appliance network and add the new MX devices to that.
In this stage all the config will already be copied with the exception that if you have a site to site autovpn, it will be disabled for this network since you would have duplicate networks.

Then once the new HA pair is online, disable the old MX'es, cable up the new ones.  Once online enable your site 2 site vpn and you are ready.

Do mind that your dynamic DNS name will be different.  So if you are using it for port forwarding or client VPN make sure the other sides are ready to change their config or if you use a DNS CNAME, adjust it.

Once online you can now proceed and merge the networks with the new appliance network and then you are ready.

[thomasthomsen]

If you remove the two previous MX from the network, and then just add the new ones, they will inherit the old MX config (perhaps not all ports, depending on how many LAN ports the different models have).

This will of course give you a little downtime when you remove the old ones.
So have a backup internet connection, like a phone hotspot, ready, so you can add the new ones to the network.
Plan for it.

Also remember to configure any static IPs on the new MX before switching.

[thomasthomsen]

PS. It can also be a good idea to wait until the two new MX are online and ready before connecting them to the LAN.

[RWelch]

MX Cold Swap - Replacing an Existing MX with a Different MX