STP Loop with Third Party Switches I manage a network mostly comprised of older Avaya ERS 3500 series switches. Recently another department has bought a package that comes with it's own server rack, 2 switches, and servers. The vendor tells me that all they need is 2 trunk ports that allow VLAN 84 to flow through. One port dedicated to SW1 and another to SW2 Every time I have plugged their switches into the server access switch, it immediately causes an STP loop and takes my network down. The problem is that another company is in charge of managing the Cisco switches that they have. I have provided a rough drawing of the setup below.
[Core(VSP)] ------------ [Server Access (ERS 3500)]==========[Unman SW 1(Cisco)] -[Unman SW 2(Cisco)]
My question is, what can I do on my server access switch to prevent the STP loop from on my end?