RSTP Backup Link
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Member Posts: 309
in CCNA & CCENT
Evening / Morning / Afternoon all,
Just finished watching one the CBT Nugget Videos on Spanning Tree. A lot of you have probably seen it also. Jeremy demonstrates RSTP in action by shutting down a root port during a Ping between PCs. The backup port the came up instantly and none of the pings were dropped at all. Is this always the case? No dropped packets?
Also can you help with understanding the following scenario.
We have 2 hosts sending data to each other. A and B
Switch D receives frame from Host A and sends it out to Host B, via its root port trunk link (fa0/2). The switch MAC table shows host B is somewhere out its F0/2 port.
FA0/2 is shutdown and RSTP backup link comes up on Switch D (Port F0/4). Does the switch know to automatically send frames for host B out of F0/4 now? Or will it flood the frame? As according to our MAC Table - Host B is supposed to be reached via F0/2 which is now down.
Hopefully that makes sense, would have been easier with a diagram I guess. I really just want to to understand what happens to frames once a link goes down, and Spanning Tree is in action. The switch MAC table would have been pointing to a certain port for all these hosts, then it suddenly goes down, so does it have to relearn everything again? If this is the case, then why did no pings drop during Jeremys live example.?
I'll try putting a diagram together as I'm getting lost in words here!
Just finished watching one the CBT Nugget Videos on Spanning Tree. A lot of you have probably seen it also. Jeremy demonstrates RSTP in action by shutting down a root port during a Ping between PCs. The backup port the came up instantly and none of the pings were dropped at all. Is this always the case? No dropped packets?
Also can you help with understanding the following scenario.
We have 2 hosts sending data to each other. A and B
Switch D receives frame from Host A and sends it out to Host B, via its root port trunk link (fa0/2). The switch MAC table shows host B is somewhere out its F0/2 port.
FA0/2 is shutdown and RSTP backup link comes up on Switch D (Port F0/4). Does the switch know to automatically send frames for host B out of F0/4 now? Or will it flood the frame? As according to our MAC Table - Host B is supposed to be reached via F0/2 which is now down.
Hopefully that makes sense, would have been easier with a diagram I guess. I really just want to to understand what happens to frames once a link goes down, and Spanning Tree is in action. The switch MAC table would have been pointing to a certain port for all these hosts, then it suddenly goes down, so does it have to relearn everything again? If this is the case, then why did no pings drop during Jeremys live example.?
I'll try putting a diagram together as I'm getting lost in words here!
Comments
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fsanyee
Member Posts: 171
Alternate and Backup ports are different!!!
In cbt nuggets videos, you can see alternate ports in work.
Backup port: if you have two or more link to the same SEGMENT (like a switch connected to a hub with redundant links)