I am currently deploying this network topology, although with a single ISP only. Using multiple switches in the WAN breakout network (VLAN) you need to keep an eye on your STP. Because I am basically implementing multiple tiered network loop, I having a problem net STP actually doing its job, and thus blocking all WAN links to my Warm Spare MX. In order to keep my secondary MX online, I have to disable RSTP on one port, so as it doesn't go into a blocking state.
... View more