Release and move ethernet ports from the old switches to the MS210 stack.
Move the LAN1/Zyxel port from the ethernet port of the last switch to the MS210 stack
Have I missed anything?
I don´t have the steps when it comes to the firewall. But I´m thinking of connecting the MX to the network through DHCP or static IP address on LAN1 and then configure as much as possible before I do the swap. Is it possible to configure DHCP range and static without turning on the feature? Can I configure NAT and rules without configure the public IP? Or should I connect the MX84 to a separate network and do the configuration before and then swap?
Couple things that I can think of off the top of my head:
1. It doesn't sound like you're that familiar with Meraki yet. I'd strongly suggest getting familiar before you start replacing the entire network of a client.
2. I believe that you'll have to create a VLAN for the second network, either the OPT or the LAN1 network. I'm guessing that the Zyxel acted the same way as pfSense acts where it has multiple NICs that are each a network, that's not how Meraki works though. You need to create VLANs for each network and then configure the ports to allow traffic on those VLANs to whichever ports are connected to whichever VLANs.
3. You can almost completely configure Meraki gear through the web portal without hooking them up before hand, when they do get online, they go up to the cloud (asuming there's connectivity) and download firmware if needed and the configuration. The only place where I believe you need to physically connect to the gear is for the MX with configuring the network details of the WAN(s) so i'd suggest that you connect a laptop or one workstation to the LAN port and nothing to the WAN port and configure that as you can't connect it to the network and tell it to have the same IP as the existing gateway (the Zyxel).
Hopefully someone else will chime in with some more thoughts.
The first steps I specify with the switches are only involving Zyxel-LAN1 and gear that is default untagged VLAN 1. The wireless OPT isn´t mention during the first switch steps. So, the first steps shouldn’t be a problem?
Yes, VLAN is needed to configure wireless that isn’t guest network. But creating VLAN can only be done when the MX is connected. That’s why I ask If somebody could give leads when it comes to the MX. Most of the stuff can be configured before setup. But I haven’t a MX to try with. As an example. According to the documentation, DHCP need to be active to be configured.
2. Turn of RTP/SRTP. (My consideration is that otherwise the new switches will interfere?)
Never this. Disabling STP because you don't understand it is absolutely the wrong move 100% of the time. When it comes to STP the right answer is to understand it, and set things up so they function properly.
If you have unmanaged switches then they will not be running STP today, so there's nothing to "interfere" with. Moreover, all versions of STP can interoperate with each other, so that's still not a concern provided they are set up properly.
Meraki implements Rapid-STP which is the 802.1w standard. There's tons fo good resources on the web for it. You really should consider giving one a read through.