STP and Link Identification

coolboarderguy · ‎10-04-2005

Hi All,

STPs job, is to indentify links and manage possible loops in redundant networks(correct me if I'm wrong). I can attach a number of switches, that aren't using vlans(meaning no trunk links) just by attaching cables to and fro. Then, of course, I can have vlan enabled switches, that are interconnected via trunk links. Does STP distinguish between the two, and how..? I'm looking for a more detailed analysis of how it does this. CCNA Intro/ICND books don't explain well the difference, if 1 exists. Cheers.

coolboarderguy...

Georg Pauwen · ‎10-05-2005

Hello,

STP does not distinguish between trunk links or access links. It listens to BPDU's (Bridge Protocol Data Units), if those are present on a port, the port will participate in the STP process. So, you could disable STP for all VLAN's on a trunk, and the trunk would not participate in STP.

Or, in CCO terminology:

Spanning-Tree Protocol (STP) prevents loops from being formed when switches or bridges are interconnected via multiple paths. Spanning-Tree Protocol implements the 802.1D IEEE algorithm by exchanging BPDU messages with other switches to detect loops, and then removes the loop by shutting down selected bridge interfaces. This algorithm guarantees that there is one and only one active path between two network devices.

HTH,

GP

coolboarderguy · ‎10-05-2005

Hi All,

fantastic stuff. Cheers.

coolboarderguy...