Multiple Spanning Tree Design Guidance
Posted on 2008-10-04
I manage a large network for a DOD agency. The network is geographically large encompassing nearly 300 Square miles. We have a mixed fiber install of MM and SM fiber, transitioning to all SM. The network started as HP only with a 9315 at the core and 2524, 4000M, and 4100 series switches. We are transitioning to all Cisco. At some point in the future we will have redundant 6509's at the core. We currently have around 200 HP and Cisco switches on our network. The 2524's and 4000M's are being replaced with Cisco 3560's, 3750's, and 4507's. We currently have 13 VLAN's.
When the HP's were deployed, Spanning-Tree was not enabled. This decision was made because it was felt a small network did not need this. As we all know this is when Spanning-Tree is established so ST issues can be addressed. As the new Network Administrator, I am faced with daily outages where soldiers/contractors bring in hubs/switches/routers and place them on the network without understanding the impact this has if they create loops.
I am starting to implement Port Security on all our switches to address this issue. More importantly, I am wanting to implement Multiple Spanning Tree (MST) on the switches that support it (the 2524's and 4000M's do not.) When the fiber infrastructure was installed, no consideration was given to network data redundancy. The fiber designers were obviously telecom engineers who home-runned all the fiber to our main telco building where our 9315 is housed. I do not have redunant paths to this building. As such, I am faced with the question of how to effectively implement MST on a building by building or switch by switch basis. Can I implement MST on a 3560/3750 in a building and create an MST region for just that building/facility?