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So let's look at rapid spanning tree protocol or ADA 2.1 w this is an evolution of the Triple E Ada

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2.1 distend.

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However Reppert spanning tree provides rapid failover and convergence times.

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The big difference that you need to remember here is that rapid spending is not based on timers like

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Ada to the one d.

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So it offers a improvement over the 30 second interval or longer that added to 1 D takes to move a port

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to the forwarding state.

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What Reppert spending tree does is it uses a bridge to bridge handshake mechanism which allows ports

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to move directly to forwarding rather than waiting for the port to move from listening to learning to

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forwarding.

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It is backward compatible with Ada to one D is transparent to end users and is standards based but it

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does introduce some enhancements including new port roll assignments and port states.

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A new BPT new format and BPT processing a bridge to bridge handshake mechanism and different topology

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change notifications and processing procedures.

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So what our port states and port roles in Ada to the one D and Reppert spending tree there are only

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three port states in rapid spending tree the learning forwarding and discarding an editor one day we

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had disabled blocking and listening.

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And these have been merged into the discarding state.

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So when you administratively disable a port that's called a disabled in to the one d but it's called

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discarding in Ada to the one w or rapid spending tree a blocking port that does not forward user data

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frames and ignores incoming data frames is called discarding an added the one w a listening port is

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not used an editor or one w a learning port is known as a learning port and a forwarding port is known

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as a forwarding port in Aden to the one w.

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So we have learning forwarding and discarding disabled blocking and listening have been merged into

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the discarding state in Ada to the one w Cisco still uses the term blocking for discarding.

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So just see those terms as interchangeable terms.

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Blocking is discarding and discarding is blocking.

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So what about port rolls.

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The role is now a variable assigned to a given port.

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Previously we had route ports and designated ports and those remain but blocking ports are now split

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into what are called backup and a turn at Port roles.

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Spending will determine the role of the port by looking at the DPD use received and deciding which one

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is more useful than another.

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A more useful BPT you is a people you that has a lower Poth cost or a better path to get to the root

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bridge.

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So let's start with a brute port with the spending tree protocol the spending tree algorithm elects

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a single root bridge for the entire bridge to network.

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Now with PV is t that's done on a per relend basis.

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But in Ada to the one d or rapid spending tree there's only one route bridge or route switch for the

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entire lead to topology the route bridge Saens people use that are more useful than the ones sent by

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any other bridge the port receiving the base to be PDU on a bridge which is known as the port.

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In other words this is the port that is closest to the route bridge.

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In terms of path cost said this typology the switches the route switch this port would be the route

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port of switch.

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And this would be the route port of switch the the route bridge it doesn't have a route port.

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All other bridges have at least one route port what is a designated port.

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This is the best port on a segment to use to get to the root bridge so old bridges connected to a given

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segment to listen to each other's PPD use and agree on the bridge sending the best people to you as

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the designated bridge for the segment.

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So in this typology this switches the route.

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So for this segment this is the designated port based port to use to get to the root bridge on this

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segment.

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This is the best port to use to get to the root bridge.

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So this is the designated port.

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Once again just imagine that you've got a PC connected to the middle of this cable which is the best

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way to get to the root bridge this way or this way.

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And as we can see this is the best path or best way to get to the root bridge.

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So this is the root port.

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It's much quicker to go this way than it is to go this way.

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So this is the designated port on this segment.

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Let's assume that we've got a hub connected here this port has been chosen as the designated port.

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And that may be because the switch here has a lower bridge ID and switch.

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And this port one which is lower than port too.

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So this is the designated port on that segment.

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Now what about alternate and backup port roles these correspond to the blocking state in Ada to the

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one d a block port is defined as any port that is not a designated Brookport a port remains blocked

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as long as it receives more useful.

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In other words better BPT use than the one it would send out on the segment therefore port must receive

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BPT use in order to stay blocked if it doesn't receive BPT use.

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It will transition to the forwarding state.

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So in rapid spending three there are two types of block ports an alternate port is a port that is blocked

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because it's receiving more useful BPT use from a another bridge on the segment.

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So in this example this port is the designated port on let's say switch B on switch.

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This port is an alternate port because more useful or better people to use are being received on this

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segment from switch B then from switch.

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And that may be because the Protea switch is lower than the property of switch a a backup port is a

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port that is blocked because it's receiving more useful BPT use from the same bridge that it's on.

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So in this example we assuming that this port this port and this port are connected to a hub.

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This port becomes the backup port.

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It's connected to the same switch as the designated port.

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But it may be a high port number before it becomes the backup port.