5 Replies Latest reply: Jan 27, 2018 3:22 AM by Daniel Dib CCIE #37149 CCDE #20160011 RSS

    How to isolate two STP domains.

    Mikey Mikey Mike

      Hi I have a really complex situation to resolve.


      We have two switch blocks separated switch blocks connected to an IP core, using a common VLAN design

      eg, Voice = VLAN2, PC_DATA=VAN3, CCTV=VLAN4 etc These switch blocks are connected to a legacy IP core.


      I have a request to install a set of servers at each site that connect to eacvhother on a common VLAN across a new MPLS core.

      My idea to use VLAN100,101,102 for three server blocks at each site and interconnect the site using two EoMPLS circuits for resiliency.

      I will only allow VLA 101,102 and native VLAN across the trunk link

      My concern is that when I bring up the two STP links my new VLANs will form the desired STP tree, but that BDPUs will cause STP to reconverge.

      Making my intersite links part of the STP tree for VLANs 2,3,4


      If I do not allow VLAN2,3,4 on my new trunk linka, does that prevent the link from becoming part of the STP tree for those VLANs, or will the two switch blocks try to form a single PVST instance for VLANs 2,3,4 essentially breaking the network?