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--- networking:spanning_tree_protocol [2020/10/25 12:25] – hvillanueva
+++ networking:spanning_tree_protocol [2020/11/05 01:05] – hvillanueva
@@ Line 64: / Line 64: @@
 {{:networking:stp_1_-_hvillanueva.png?250|}}
+===== LABORATORY =====
+{{:networking:stp_2_-_hvillanueva.png?600|}}
+All switches in the above topology are assumed to have the same priority.
+So, we know that the first step is to choose the RB. To do this, having all the same priority, the algorithm chooses the one with the lowest MAC address, which turns out to be SW3.
+{{:networking:stp_3_-_hvillanueva.png?600|}}
+The next step is to find the minimum path from each switch to the RB.
+Starting with SW2 we see that it has two ports that allow us to reach the RB. For port 5 as well as for port 17 the total cost is 19, the result of 100 Mbps links. In this case, port 5 is chosen as root and it will go to FWD status, while port 17 would remain as non-port. designated. Port 17 goes to the listening state (LST), as the switched next hop has been put to the blocked state (BLK). The reasons why this last case will be seen when we analyze SW1.
+{{:networking:stp_4_-_hvillanueva.png?600|}}
+{{:networking:stp_5_-_hvillanueva.png?600|}}
+In the case of SW1, we observe that it has two ports that allow us to reach the RB. For port 7 the total cost is 38, the result of adding 19 of the 100 Mbps direct link plus 19 of the link that is accumulated from the previous 100 Mbps switch (accumulated values to reach the RB through this route) and for port 1 with a total cost of 19 (since it has a direct connection with the RB by this route). In this specific case, the port with the smallest cost value is chosen, which is port 1. In this way, port 1 will be the root port (Designated) and will go to FWD status and port 7 will remain in status (BLK) locked.
+{{:networking:stp_6_-_hvillanueva.png?600|}}
+{{:networking:stp_7_-_hvillanueva.png?600|}}
+In the event that port 1 fails, SW1 port 7 will automatically reactivate, changing its state from BLK to LST state (listening), then to LRN state (learning) and finally to FWD state (forwarding). . These changes in SW1, causes it to have repercussions in SW2, where port 17, which was in the LRN state (learning), would automatically go into the FWD state (forwarding), thus leaving the entire network operational.
+ --- //[[ing.hvillanueva@gmail.com|Humberto Villanueva]] 2020/11/05 01:05//