So let's look at rapid spanning tree protocol or ADA 2.1 w this is an evolution of the Triple E Ada
2.1 distend.
However Reppert spanning tree provides rapid failover and convergence times.
The big difference that you need to remember here is that rapid spending is not based on timers like
Ada to the one d.
So it offers a improvement over the 30 second interval or longer that added to 1 D takes to move a port
to the forwarding state.
What Reppert spending tree does is it uses a bridge to bridge handshake mechanism which allows ports
to move directly to forwarding rather than waiting for the port to move from listening to learning to
forwarding.
It is backward compatible with Ada to one D is transparent to end users and is standards based but it
does introduce some enhancements including new port roll assignments and port states.
A new BPT new format and BPT processing a bridge to bridge handshake mechanism and different topology
change notifications and processing procedures.
So what our port states and port roles in Ada to the one D and Reppert spending tree there are only
three port states in rapid spending tree the learning forwarding and discarding an editor one day we
had disabled blocking and listening.
And these have been merged into the discarding state.
So when you administratively disable a port that's called a disabled in to the one d but it's called
discarding in Ada to the one w or rapid spending tree a blocking port that does not forward user data
frames and ignores incoming data frames is called discarding an added the one w a listening port is
not used an editor or one w a learning port is known as a learning port and a forwarding port is known
as a forwarding port in Aden to the one w.
So we have learning forwarding and discarding disabled blocking and listening have been merged into
the discarding state in Ada to the one w Cisco still uses the term blocking for discarding.
So just see those terms as interchangeable terms.
Blocking is discarding and discarding is blocking.
So what about port rolls.
The role is now a variable assigned to a given port.
Previously we had route ports and designated ports and those remain but blocking ports are now split
into what are called backup and a turn at Port roles.
Spending will determine the role of the port by looking at the DPD use received and deciding which one
is more useful than another.
A more useful BPT you is a people you that has a lower Poth cost or a better path to get to the root
bridge.
So let's start with a brute port with the spending tree protocol the spending tree algorithm elects
a single root bridge for the entire bridge to network.
Now with PV is t that's done on a per relend basis.
But in Ada to the one d or rapid spending tree there's only one route bridge or route switch for the
entire lead to topology the route bridge Saens people use that are more useful than the ones sent by
any other bridge the port receiving the base to be PDU on a bridge which is known as the port.
In other words this is the port that is closest to the route bridge.
In terms of path cost said this typology the switches the route switch this port would be the route
port of switch.
And this would be the route port of switch the the route bridge it doesn't have a route port.
All other bridges have at least one route port what is a designated port.
This is the best port on a segment to use to get to the root bridge so old bridges connected to a given
segment to listen to each other's PPD use and agree on the bridge sending the best people to you as
the designated bridge for the segment.
So in this typology this switches the route.
So for this segment this is the designated port based port to use to get to the root bridge on this
segment.
This is the best port to use to get to the root bridge.
So this is the designated port.
Once again just imagine that you've got a PC connected to the middle of this cable which is the best
way to get to the root bridge this way or this way.
And as we can see this is the best path or best way to get to the root bridge.
So this is the root port.
It's much quicker to go this way than it is to go this way.
So this is the designated port on this segment.
Let's assume that we've got a hub connected here this port has been chosen as the designated port.
And that may be because the switch here has a lower bridge ID and switch.
And this port one which is lower than port too.
So this is the designated port on that segment.
Now what about alternate and backup port roles these correspond to the blocking state in Ada to the
one d a block port is defined as any port that is not a designated Brookport a port remains blocked
as long as it receives more useful.
In other words better BPT use than the one it would send out on the segment therefore port must receive
BPT use in order to stay blocked if it doesn't receive BPT use.
It will transition to the forwarding state.
So in rapid spending three there are two types of block ports an alternate port is a port that is blocked
because it's receiving more useful BPT use from a another bridge on the segment.
So in this example this port is the designated port on let's say switch B on switch.
This port is an alternate port because more useful or better people to use are being received on this
segment from switch B then from switch.
And that may be because the Protea switch is lower than the property of switch a a backup port is a
port that is blocked because it's receiving more useful BPT use from the same bridge that it's on.
So in this example we assuming that this port this port and this port are connected to a hub.
This port becomes the backup port.
It's connected to the same switch as the designated port.
But it may be a high port number before it becomes the backup port.