STP blocking ports election

[ppreiato13279]

Hi everyone. I'm studying for the CCNA and to learn STP elections I'm doing some excercises using packet tracer. I'm using a 6 switches mesh topology and try to see which port would be the designed port or blocking port. Now, when all the links have the same speed it's easy to determine DP and Blocking ports. The problem is when I use different links: gigabith and fastethernet links. How do I determine DP and Blocking Ports in this exercise? Can you explaine me how to do it right? In the file attached you can see the topology I'm talking about. Straight cables are gig links, crossed cables are fastethernet links. The Bridge priority is the standard one. Please help me, I'm going crazy ahah. Thank you everyone.

[rais]

STP does take into consideration Path Cost, GE port will have a better (lesser) cost than the FE, so a GE port will be chosen above FE port.

HTH.

[Martin L]

Hi, welcome. this depends on 3 major factors. Bridge priority, main MAC address of switch, Costs.  The process is (in sequence): Root sw election, Root Port elections, Designated ports and then blocking ports elections.  If priority is same (default), then lower MAC wins. To determine which ports are which switches use lowest cost to reach Root Sw.

IF PT has issues moving traffic is because Your topology is too complex. PT is just a software sim, not real IOS. Also, exam and real life designs will have more simpler topology, like 4 switches square shaped topo (with or w/o cross-over links).  To understand STP I would start with simply 3 switches in a triangle topology before moving to 4 switches.

I would go to CLN CCNA forum for learning networking.  CLN is focus on Certs topics, learning technologies (mostly for exams but not always) and exam/cert issues.  You get replies from fellow learners like you and me.  This forum here is focus more on real life issues and technologies beyond exam topics.  Of course, you can post your questions here or in both places.

https://learningnetwork.cisco.com/s/topic/0TO3i0000008jYHGAY/ccna-certification-community

or see all discussions at https://learningnetwork.cisco.com/s/discussions

Regards, ML
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