So let's have a look at spanning-tree show spanning-tree VLAN 1, notice we see a difference
here we see a port channel.
One thing to notice here is notice ports such as gigabit 1 0 1 and 1 0 2 1 0 3 are point to point spanning
tree links.
Whereas the port
channel is a shared spanning tree link.
Now for the real world,
typically once you've put interfaces into the port-channel you do the configuration on the port-channel.
However, if you have problems do the configuration in the port channel and then verify that the configuration
has also been applied to the physical interfaces.
If it's not applied to the physical interfaces do the config on both the port channel and the physical
interfaces to ensure that the configuration is correct
but typically you only need to do the configuration on the port-channel. So I'll show you that here when
I do the configuration on the physical interface it's not applied to the port-channel but configuration
applied to the port-channel is pushed down to physical interfaces.
That's how it should work.
Sometimes in the real world, you'll have problems with that. To optimize spanning tree,
what we want to do on those ports is specify spanning tree link type point to point that we'll make
rapid spanning-tree converge quicker shared links are typically used down to hosts or to hubs but we've
got switches here.
So we wanna make the spanning-tree link-type point to point to make it converge quicker.
So show spanning tree VLAN 1.
Now notice I did the configuration on the physical interfaces what I need to do actually is do that
on the port-channel. So spanning tree link type point to point and then I'll do something similar on
this side interface port,
channel 1 spanning-tree link-type point to point and let's see if that's made a difference.
So show spanning-tree VLAN 1 that looks better notice the port channel is showing us point to point.
Okay, so this looks good on this side show spanning-tree VLAN 1 notice on switch 2 no ports are blocking,
previously one of the ports on switch 2 was blocking for VLAN 1.
In other words, previously gigabit 1 0 24 was blocking but it's not blocking at the moment because
that port is part of the port channel.
Notice also the cost of the port channel is lower than other physical interfaces because this is a better
interface.
It's got 2 gigabit ports that make up the channel rather than just a single gigabit port. On this side
show spanning tree VLAN 10.
Now notice here we don't see VLAN 10 propagated across the port channel.
Again, if you have problems like this where configuration is done on the physical interface but is not
shown on the port-channel, type these commands on the port-channel.
So typically once you put your interfaces in a port-channel you do the configuration on the port-channel.
Interface port channel 1, switch port mode trunk, switch port trunk we have to separate encapsulation
first, so switch port trunk encapsulation dot1q switch port mode trunk.
So notice now the configuration is shown on the port-channel
and notice when I use the command show spanning-tree VLAN 10, I still don't see the port-channel because
on this side we're getting an error with inconsistent port-channel information. We have to configure the
commands on the port channel. So interface port
channel 1, switch port trunk encapsulation, dot1q switch port mode
trunk.
So we need to ensure that we have the commands on the port-channel as well as on the physical interface.
Once you add your physical interfaces to the port-channel, you do your configuration on the port-channel
rather than on the physical interfaces. So let's verify the port-channel by using these show interfaces
port-
channel 1 status command.
Notice we told at the moment that the port channel is not connected.
So what I'll do is shut the interfaces down.
This is one thing to remember with port-channel.
It's better to make all your changes while the interfaces are shut down and then no shut them
once you've completed your changes.
If you have any inconsistency, shut the interfaces down and bring them up again to double check things.
Okay, so let's confirm the configuration, on switch 1 that looks good, on switch 2.
We need to make sure that everything is the same.
So both sides look good there.
This configuration is configured on both sides
and the physical interfaces match that configuration on both sides. So show spanning-tree VLAN 1,
port-
channel is forwarding so that's good, show spanning-tree VLAN 1, at the moment
we still have a status of learning that should hopefully go to forwarding very soon.
There you go,
it's forwarding.
Show ether channel,
port-channel shows us that the interfaces are active. Show spanning-tree VLAN 10 notice now we
can see that VLAN 10 is forwarding on the port-channel.
Same is true for VLAN 20, same is true for VLAN 30 and the same is true for VLAN 100. On this side
show spanning-tree or VLAN 10 still needs to go to forwarding on this side.
So we need to just give it some time but you can see there is an example, 100 is forwarding, VLAN 1 is
forwarding, VLAN 10 is now forwarding, VLAN 20 is now forwarding and VLAN 30 is now forwarding.
So on all VLANs on both sides, the switches are forwarding on all ports this is what you want to have
in the core of your network, you don't want to have your core switches blocking, blocking ports should
be on the access switches. So as an example on access 1 shows spanning-tree VLAN 1, one of the ports
is blocking and we know which port is blocking, it's gigabit 1024
and the reason why is that we've made core 1 the route, core 2 is the backup route. So this port should
be blocking. What about for VLAN 10? This port is also blocking, VLAN 100, 23 is blocking
because we made core 2 the route. Now we saw the LEDs go orange but they've now gone back to green because
packet tracer has updated the spanning-tree network so again we can see that the switch is forwarding
on all VLANs. So as I demonstrated in this video you can have problems if there's a mismatch or mis
configuration between the port channel and the physical interfaces. The recommendation is to make sure
that the configuration is the same on both sides make sure that the configuration of both the logical
interface.
In other words, the port channel and the physical interfaces are the same on both sides. So make sure
that this matches this, but also make sure that this matches the configuration of the port-channel on
the same switch as well as on the other switch.
So, essentially everything should be a mirror image.
Make sure that this matches this, makes sure that this matches this.
If you have problems like I had here shut the physical interfaces down confirm all the configuration
and then no shut the physical interfaces.
Hope that helps you for both the exam and for the real world.