RSTP Question from Switch Foundation Learning

Forgive me if this is a terrible question, but a diagram in the switch foundation learning book has me a little confused. According to what I thought and everything I can find, there can only be one designated port per segment in RSTP. According to this diagram (comes from the book), there are 2 DP between sw3 and sw5 (the switches weren't labeled in the book, I did so for clarification), which I thought was classified as 1 segment.

Am I incorrect in my understanding that only 1 DP per segment allowed?

Or...

Am I incorrect in my assumption that the two links between sw3 and sw5 is one segment?

Or...

Or is this just a typo and the right port on SW3 is something besides a DP, in which case, what type of port is it?

I put the diagram in an attachment, but the actual diagram is on p.128 in Chapter 3 of the Switch Foundation Learning Book. Thanks in advance!

diagram.JPG

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Comments

Heero

larue38462 wrote: »

Forgive me if this is a terrible question, but a diagram in the switch foundation learning book has me a little confused. According to what I thought and everything I can find, there can only be one designated port per segment in RSTP. According to this diagram (comes from the book), there are 2 DP between sw3 and sw5 (the switches weren't labeled in the book, I did so for clarification), which I thought was classified as 1 segment.

Am I incorrect in my understanding that only 1 DP per segment allowed?

Or...

Am I incorrect in my assumption that the two links between sw3 and sw5 is one segment?

Or...

Or is this just a typo and the right port on SW3 is something besides a DP, in which case, what type of port is it?

I put the diagram in an attachment, but the actual diagram is on p.128 in Chapter 3 of the Switch Foundation Learning Book. Thanks in advance!

They are not one segment. One segment in this type of scenario would be a bus type situation, which you will probably never see in ethernet networks.

peanutnoggin

larue38462 wrote: »

Forgive me if this is a terrible question, but a diagram in the switch foundation learning book has me a little confused. According to what I thought and everything I can find, there can only be one designated port per segment in RSTP. According to this diagram (comes from the book), there are 2 DP between sw3 and sw5 (the switches weren't labeled in the book, I did so for clarification), which I thought was classified as 1 segment.

Am I incorrect in my understanding that only 1 DP per segment allowed?

Or...

Am I incorrect in my assumption that the two links between sw3 and sw5 is one segment?

Or...

Or is this just a typo and the right port on SW3 is something besides a DP, in which case, what type of port is it?

I put the diagram in an attachment, but the actual diagram is on p.128 in Chapter 3 of the Switch Foundation Learning Book. Thanks in advance!

I think in the book, the author is referring to one point-to-point ethernet link as a segment. Remember, in spanning-tree, all ports connected to another switch participates in spanning-tree and are individual segments because spanning-tree's job is to prevent bridging loops between the switches. So in that case between those two switches, since the links are not an etherchannel, they are regarded as two different segments, therefore one switch has to have two designated ports and the other is going to have one root port and one blocking port (the blocking port prevents a loop). HTH.

-Peanut