STP/MSTP question

Sorry for yet another spanning tree question. I've done a bit of homework but I just want to make sure I fully understand the required configuration.

What's maybe slightly unique in our situation is we don't have any control of the two upstream switches which are owned by our ISP.

It is important that the root bridge is owned by our ISP.

We have two switches with a configured 2 port LAG between them. We have a single uplink from each of our switches to our ISP switches.

The issue is we need to enable spanning tree for our internet VLAN only. We pass other VLAN's on the LAG which do not need to partake in spanning tree.

The uplinks to our ISP are access ports passing one VLAN.

We haven't stacked the switches as we need to be able to run firmware updates independently of each other.

So these are the options we are looking at

1. I could create another LAG just for the Internet and use normal STP/RSTP but this is an expensive use of 10 GB ports.

2. Use MSTP? The problem with this we will need to use the same VLAN ID's and region settings as our ISP. Could be something we could arrange but not something I am totally confident in maintaining

My gut instinct is just to go with option 1. I don't really need redundancy on this as in normal operation the link isn't required. It will only be used if one of our ISP switches dies which is covered under an SLA.

Or I just lose two ports on each of our switch, not ideal, but not the end of the world either.

Any thoughts on this or other suggestions would be greatly apprecaited

At another location we do have switches which support PVSTP which I think would be a better fit, but that's a question for the IBM forum