In this topology, I have two switches which are configured to run PVS.
RT Not rapid PVS plus, but simply PVS.
I'll show you that config in a moment.
Rather, one is connected to switch one and router two is connected to switch two, and the routers
are simply acting as edge devices or PCs in this topology.
I've also got a hub connected to switch one and switch to.
His switch one show run pipe include.
Span.
As you can see at the moment, the switch is configured for PV ist.
I'll explain the extended system ideas in more detail later.
But essentially it means that the priority of the switch is based on the priority and VLAN number.
So as an example, show spanning tree.
The switch has a bridge ID consisting of the property 32769, which is the default of 32768 plus the
extended system ID of one because we're looking at a VLAN one and MAC address of the following.
The switch is currently the route.
What I want you to see is that the spanning tree enabled here is a triple E.
So in this output it looks like you're running at a 2 to 1 dx, but actually the switch is configured
for per VLAN, spanning tree per VLAN, spanning tree is compatible with ADA 2 to 1 DX switches and
therefore we can see triple E in the output here.
His switch to.
So run pipe include span.
Switches configured to use PV ist.
Extended system IDs are being used.
On the switch.
The bridge ID consists of the property three, two, seven, six and nine, which is 32768.
The default plus the VLAN number, which is VLAN one in this example.
This is the MAC address of the switch.
So we have two switches.
One has this MAC address.
One has this Mac address.
Switch.
One has become the root of the spanning tree because it has a lower Mac address when compared to the
switch.
So because of the Lower Mac address notice AC is lower than E in hexadecimal switch one became the root
of the spanning tree.
What you'll also notice is that on switch one, all ports are forwarding in the topology.
The ports that are currently connected are those ports and they all forwarding.
On switch to however port one which is gigabit is zero zero is the root port and its forwarding has
a path cost of four gigabit.
Zero one is blocking or discarding to use the industry standard term port two 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 were determined, let's have a look at the beads.
So to start a CAPTCHA on that link and what we can see here in Wireshark is a spanning tree BPU.
So it's using 82.3 Ethernet frames.
Notice the destination address is the well-known MAC address for Spanning Tree.
It is a multicast broadcast address from this Mac address.
Yes.
Which one?
Notice the MAC address of the switch is zero zero 11 C six ac d d and we currently looking at port three
on the switch.
So notice d00, but this is dd03.
Because in spanning three, that's the port that we currently looking at.
If we went and looked at Port two as an example.
Notice the Mac address ends in zero two.
We've got port 000102 and zero three.
So back in Wireshark.
He has a capture sent out of Port three.
In spending tree.
We can see the spending tree version.
So this is spending tree is zero because in this port it's actually using ADA 2 to 1 DX or the original
version of Spending Tree.
The root identifier is 32768.
There's the VLAN number and there's the MAC address of the switch.
Which we can see clearly here.
So notice route identifier.
There's the information of 32768.
VLAN one.
There is the mac address of the switch.
The route path cost is zero because this switch is the route.
So there's no cost to get to the route.
There's the port identifier and here are some timers used in spanning tree.
Now when a switch boots up, all ports are put into the blocking state.
They then move to other states based on timers in a 2 to 1 D.
When a spending tree switch boots up, all ports are put into the blocking state.
After 20 seconds called the max age timer, ports move to what's called the listening state.
If a switch is already 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 duration and after 15 seconds, ports transition
from the learning state to the forwarding state.
So an editor of one RD or PVS ist, it can take 50 seconds for ports to start forwarding on switches
because they move from blocking to listening to learning to forwarding.
Now in the listening state they are sending beep to use but not updating their mac address tables.
In the learning state beeps are sent and the MAC address tables of switches are updated, so only if,
based on the spanning 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, or typically if a switch
is already up and you plug an A cable into that switch after 30 seconds, the port will start forwarding.
So in the BPD queue we 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 hello timer.
In other words, BPU hellos are sent out every 2 seconds.
The max age time is 20 seconds and the forwarding delay timer is 15 seconds.
And that's what we see in the BPAs as captured in our topology.