In this typology I have two switches are which are configured to to run previous t not rapid previously
plus but simply previous t.
I'll show you that config in a moment.
Rodda one is connected to switch 1 and router 2 is connected to switch 2 and the rods are simply acting
as edge devices or PCs in this topology.
I've also got a hub connected to switch one and switch to just switch one show run pipe include spanne
as you can see at the moment the switches is configured for previous t well-explained extended system
IDs in more detail later.
But essentially it means that the priority of the switches based on the priority and a villain number.
So as an example shows spending tree the switch has a bridge ID consisting of the priority 3 2 7 6 9
which is the default of 3 2 7 6 8 plus the extended system id of one because we are looking at a villain
one and MAC address of the following.
The switch is currently the route.
What I want you to see is that the spending tree enabled here is I triple E.
So in this output it looks like Im running a two to one D but actually the switch is configured for
Poovey LAN spending tree povi and spinning tree is compatible with Ada 2 to 1 D switches and therefore
we can see Triple E and the output here has switched to show run type.
Include spanne which is configured to use PV is t extended system IDs are being used
on the switch.
The bridge idea consists of the property 3 to 7 6 and 9 which is 3 2 7 6 8 2 the default plus the villain
number which is veel and 1 in this example.
This is the MAC address of the switch.
So we have two switches.
One has the MAC address.
One has the MAC address so which one has become the root of the spending tree because it has a lower
MAC address when compared to the switch.
So because of the lower MAC address notice a c is lower than E-A in hexadecimal.
So which one became the root of the spanning tree what you also notice is that on switch 1 all ports
or forwarding in the topology the ports that are currently connected are those ports and they all forwarding
on switch to however Pt. 1 which is gigabit 00 is the root port and it's forwarding has a path cost
of four gigabit.
0 1 is blocking or discarding to use the industry standard term.
Pt. 2 is forwarding port three is blocking.
So this port is also blocking route switches forward on all ports.
Before I show you how port status is determined Let's have a look at the BBC's
historic capture on that link and what we can see here in Wireshark is a spanning tree BPT.
So it's using a two or three Ethernet Frayne's.
Notice the destination address is the well-known Mac address for spending tree it is a multi-course
broadcast address from the Mac address.
Yes which one notice the Mac address of the switch is 0 0 11 C 6 a c d d and we currently looking at
ports 3 on the switch.
So I notice Didi's 0 0 but this is Didi's 0 3 because in spending tree that's the portal we currently
looking at if we went and looked at port 2 as an example
notice the Mac address ends in 0 2.
We've got port 0 0 0 1 0 2 0 3.
So back in Wireshark he has our capture sent out of Port three in spanning tree we can see the spanning
tree version.
So the suspending tree is 0 because in this port it's actually using Ada 2 the one d or the original
version of spanning tree the route identifier is 3 2 7 6 8 is the villain number and there's the Mac
address of the switch which we can see clearly here.
So notice route identifier is the information of 6:57 6:8.
Villain 1 there is the Mac address of the switch.
The root path cost is zero because the switch is the root.
So there's no cost to get to the root base.
The port identifier and here all some time is used in spending tree.
Now when a switch boots up all ports are put into the blocking state they then move to other states
based on time as an aid to the one D when a spending tree switch boots up all ports are put into the
blocking state off to 20 seconds called the max a timer ports move to what's called the listening state.
If a switch is ready up and you connect a cable to the port.
In other words the link goes up.
It starts at the listening state.
Ports will then move to the learning state based on the forward delay which is 15 seconds in generation
and after 15 seconds Portes transition from the learning state to the forwarding state.
So an edit to the one d or PV t it can take 50 seconds for ports to start forming on switches because
they move from blocking to listening to learning to forwarding.
Now in the listening states they are sending BPT use but not updating their mac address tables in the
learning state BPT use a.
And the MAC address tables of switches are updated.
So only if based on the spending tree calculation it's determined that a port can be opened a port is
set to the forwarding state after 50 seconds when a switch comes up.
Typically if a switch is already up and you plug the cable into that switch after 30 seconds the port
will start forwarding.
So in the PPD you can see the max age timer and the forwarding delay timer.
This is determined by the route bridge.
So on switch one which is the route bridge we can see that the holloed timer.
In other words BPT Hello's are sent out every two seconds.
The max age time is 20 seconds and the forwarding delay timer is 15 seconds.
And that's what we see in the BPT use as captured in our typology.