We currently have two MX84 firewalls setup with a 1GB connection (I know with the mx84 we only get 500MB but we get a real good price on the 1GB - $0)
We are in the process of adding a backup ISP but it is going to be limited. and we only want it to be used as a last resort. From reading the order of failover is
Primary - WAN 1
Primary - WAN 2
Secondary - WAN 1
Secondary - WAN 2
So if we only plug the device in to the Secondary would this achieve what we want or are there any issues to be considered.
Yes.
But how many times the secondary mx wan1 would still work if the primary wan1 is down. I guess only when there is a bad cable.
That ordering is correct.
It's explained here (including Cellular backup):
I have been putting some thought in to this and was wondering if either of these would work. I only want to use ISP 2 as a last resort since it is a cellular device connected to the WAN port.
I don't have test environment to try this.
Primary WAN 1 - ISP 1
Primary WAN 2 - ISP 1
Secondary WAN 1 - ISP 1
Secondary WAN 2 - ISP 2
or
Primary WAN 1 - ISP 1
Primary WAN 2 - no used
Secondary WAN 1 - ISP 1
Secondary WAN 2 - ISP 2
Haven't tested it but from a logical perspective it shoud work. At least if MX1 does'nt have WAN2 to fail over, there's no other chance than to fail over to MX2.
I would go with the secondary setup there
Primary WAN 1 - ISP 1
Primary WAN 2 - no used
Secondary WAN 1 - ISP 1
Secondary WAN 2 - ISP 2
So I ran a test on the weekend using the following
Primary WAN1 - ISP1
Primary WAN2 - ISP2
Secondary WAN1 - ISP1
Secondary WAN2 - not used.
This did work. There is an issue though. When I tried to force a failover from the Secondary to the Primary using the dashboard I got a message stating that I needed to configure the WAN2 port and it would not let me switch. I had to go in and unplug the cell device, force the failover and plug it back in.
Next I have to try
Primary WAN1 - ISP1
Primary WAN2 - ISP1
Secondary WAN1 - ISP1
Secondary WAN2 - ISP2 - we want this as a last resort