Sunday, November 27, 2016

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Rapid-PVST+ Configuration

                             Now the, we talked about the Theory of Rapid-PVST+, let’s see how to set it up, first let’s see
                How to change STP mode to Rapid-PVST+, to do that go to Switch Global Configuration Mode
Ø  Sw1(config)#spanning-tree mode rapid-pvst
Ø  Sw2(config)#spanning-tree mode rapid-pvst
Ø  Sw3(config)#spanning-tree mode rapid-pvst
Now our switches are running Rapid-PVST+, and they should be able to Convergence more quickly, we can confirm that we indeed are in Rapid-PVST+ Mode by saying
Ø  Sw1#show spanning-tree summary
                   And it says that the Switches in a Rapid-PVST Mode and remember, if our trunks are DOT1Q trunks that means we doing Rapid-PVST+, but it looks we running Rapid Spanning Tree Protocol for all our Vlan’s like we did with other Spanning Tree Protocol Variants, if we want to make Switch Sw1 the Root for Vlan’s 100 and 300, we can do that
Ø  Sw1(config)#spanning-tree vlan 100,300 root primary
Primary Root for Vlan’s 100 and 300, and we want to be secondary Root for Vlan 200
Ø  Sw1(config)#spanning-tree vlan 200 root secondary

Let’s go to Switch Sw3 and we say that, we want to be the Primary Root for Vlan 200
Ø  Sw3(config)#spanning-tree vlan 200 root primary
And we want to be the Secondary Root for Vlan’s 100 and 300
Ø  Sw3(config)#spanning-tree vlan 100,300 root secondary

And to confirm this, we can do
Ø  Sw3#show spanning-tree summary

And we can see that we are the Root for Vlan 200 and on Sw1 reissue the command.
Ø  Sw1#show spanning-tree summary
We see that, we are the Root for Vlan’s 100 and 300.
 Now let’s assume on one of these Vlan’s and take a look at different link-type we have, let’s do a
Ø  Sw1#show spanning-tree vlan 300
                           And because this is the Root for Vlan 300, you see the Port Roles is Designated Port for each of these Port’s meaning that our status is Forwarding, and the link-type are P2P, Point-to-Point, and the reason these link-type are Point-to-Point is that the Switch made that determination automatically by looking at Duplex of these ports, if we have a port in Full Duplex mode the assumption by the Switches is, we probably connected to a another Switch or may be a Router, and that’s gonna make the link-type P2P, if we were in Half Duplex Mode the Switches going to assume that we connected to a shared media segment, maybe we connected to an Ethernet Hub and that case link-type would be a Shared.
                        But here is a challenge may be, we connected to an End User Station like a PC or here we have a Phone plugged in a fastethernet 1/0/10, and that means fastetherent 1/0/10 should be considered an Edge Port, how we say that Port is an Edge Port.
If we wanted to specify that, this was a Shared link-type, instead of P2P link-type, here we can do that
Ø  Sw1(config)#interface fastethernet 1/0/13
Ø  Sw1(config-if)#spanning-tree link-type
                  Notice here, we have two option Point-to-Point and Shared, but there is no Edge Port option, we can do that to Shared, but I want to show you another approach to that.
Ø  Sw1(config-if)#duplex half
Ø  Sw1(config-if)#end

When we set Duplex to Half Duplex, let’s reissue the command on Sw1
Ø  Sw1#show spanning-tree vlan 300
                 Now look at this it’s says that the link-type is now Shared, the Switch assume that we are connecting into a Shared media Ethernet Hub, and we also want to change fastetherent 1/0/10 to be an Edge Port that connected to a IP Phone, let’s say that is an Edge Port, here we can configure that
                     We going to enable a feature, we going to be talking about more in our upcoming Topic, but its’ called Portfast, instead of plugging in a device to Switchport and waiting through the Listening and the Learning states before we transition to a Forwarding.
                   If we go into a port and say “spanning-tree portfast”, we telling that Switchport to “Mr. Switchport, we promise that we are connecting to you an End Devices”, it’s not something short of Switch that’s going to send any BPDU’s, it’s an End Station and as a result, please do not wait through the Listening and Learning State, here how we do that
Ø  Sw1(config)#interface fastethernet 1/0/10
Ø  Sw1(config-if)#spanning-tree portfast

And now use show command
Ø  Sw1#show spanning-tree vlan 300
                 And now look at this, this time it’s says this is an Edge Port, meaning that when we plugged that IP Phone into a Switch Sw1 fastetherent 1/0/10 interface, it doesn’t have to wait that 30-second’s period of time to Transition from Listening to Learning to a Forwarding.
                       It’s going to go active almost immediately and by the way, we do not have to be running Rapid-PVST+ and order to use that Portfast feature, that can be used with any of our flavors of Spanning Tree Protocol and we gonna be talking more about portfast in upcoming session.
             What this session done, is shown us how to very easily enable Rapid-PVST or Rapid PVST+ on our Cisco Catalyst Switches, we saw that we can influence Root Bridge Selection exactly as we done before, and we saw that Rapid-PVST or Rapid-PVST+ would attempt to automatically determine the appropriate link-type based on Duplex settings but we could go in and override that default settings, we would set the link-type to P2P or Shared. and we could also say that the Port was an Edge Port by enabling Portfast on that Port.

Join me on our next upcoming session about

Ø  Uplink Fast
Ø  BPDU Guard
Ø  Backbone Fast
Ø  BPDU Filter
Ø  Port Fast
Ø  Root Guard

Ø  Loop Guard

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1 comment:

  1. Great Article
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