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Now to improve Spanning Tree performance

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we want to make these ports point-to-point Spanning Tree ports

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point-to-point Spanning Tree ports converge a lot quicker

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when using Rapid Spanning Tree.

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At the moment on our switches such as switch 3

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we can see that the ports are shared ports

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they're going to take a lot longer to converge

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So intrange gigabit 0/0 - 1 spanning-tree link-type point-to-point

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This will allow Spanning Tree to converge a lot quicker

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notice the ports are now point-to-points links.

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That’s typically determined by the speed and duplex

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at the moment these switches in a lab are set to auto-negotiates speed and duplex

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you might want to hard code some of those options

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if a port is set to full duplex

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It will become a point-to-point port in Spanning Tree

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as you can see here forVLAN 10, gigabit 0/0 and 0/1 are point-to-point links

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but gigabit 0/2 is a shared link.

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sh int g0/2

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shows me that we're using auto duplex, auto speed negotiation.

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In a physical network, we may want to hardcode speed and duplex

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or when it negotiates to use full duplex, the port will become a point-to-point link.

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But here in GNS3 it's not negotiating that.

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So I want to manually set the port type to point-to-point in Spanning Tree.

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So let’s do the same in all switches.

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So switch 4 sh spanning-tree vlan 20 as an example

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you can see the port are shared

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so int range g0/0 - 1

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on the uplinks tpanning-tree link-type point-to-point

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sh spanning-tree vlan 20

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notice those ports are now point-to-point

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and let’s do it on the core switches as well.

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So at the moment sh spanning-tree vlan 1

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all my ports have a type of shared including the link aggregation.

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So int range g0/0 - 3 spanning-tree link-type point-to-point

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sh spanning-tree vlan 1 as an example

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ports are still showing as shared on some of the ports

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gigabit 1/0 is the link to the host that’s OK.

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Port channel is showing up as shared

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so I'll go into the port channel

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and let's configure that as a Spanning Tree point-to-point link.

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sh spanning-tree vlan 1

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all ports are now point-to-point on the core.

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So these links all point-to-point

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we'll do the same on switch 2.

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So int range g0/0 - 3 spanning-tree link-type point-to-point

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int port channel 1

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make it point-to-point sh spanning-tree vlan 1

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all ports are point-to-point this port is still shared

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so I could make that a point-to-point link

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but for the moment I’m going to leave that as it is

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because we can enable PortFast on these links

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to increase the throughput of Spanning Tree convergence on those ports.

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So sh spanning-tree vlan 10 and vlan 20

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now, let’s test some of the convergence

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I’m going to send a continues ping from PC 1

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so router 1 pretending to be our PC to the core switch

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and let see how good the convergence is

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so on router 1 ping 10.1.10.1 ping succeeds

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but I can repeat the ping let say 10,000 times

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before I press enter on switch 3

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so this switch here sh spanning-tree vlan 10

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we can see that the root port is gigabit 0/0

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this port is an alternate port

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so we'll stop the ping, conf t int g0/0 shut it

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notice we’ve lost the ping losing a few pings here

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so the convergence is taking a while

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one of the pings we can do to speed up convergence is change this port

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notice the state is learning

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gigabit 0/1 has gone forwarding already

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but notice this port is still learning.

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Because it’s a shared port it’s gonna take longer to converge

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so it took a while for that port to converge

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it could take like 30 seconds for it to converge

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so point-to point links converge very quickly.

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As an example, when I shut this port down

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this port very quickly went to the forwarding state

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if I no shut that port again

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sh spanning-tree vlan 10

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you can see that port is already forwarding

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so very quickly this port went to forwarding

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and this port went to blocking

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but the problem is the port to the host is blocking because this is a shared port.

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So shared ports goes through the normal Spanning Tree timers

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of blocking, listening, learning forwarding

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so it's gonna take it a while for the port to start forwarding.

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Notice we're learning now and then after a period of time its starts forwarding.

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So if you don’t have a switch connected to this port

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you can improve the convergence of that port

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by making it a Spanning Tree Portfast port

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so I could specify Portfast here

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notice we're warned that this should only be enabled on ports

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where we don’t have switches connected

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so we shouldn’t have hubs or switches or other devices

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that can cause loops in the network on these ports.

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So our pings are continuing.

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sh spanning-tree vlan 10

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shows me that the port is a shared port

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but now when I go into gigabit 0/0

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and shut the port down, ports gone down now

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notice gigabit 0/1 is already forwarding it's taking a while

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because I put, its look like I put the command on the wrong port

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so let’s have a look again at the config.

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I incorrectly configured Portfast on gigabit 0/0

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so let’s fix that problem

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so int g0/0 no spanning-tree portfast edge

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do sh run in g0/0 no shut the port now

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and then let’s go on to gigabit 0/2

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and type spanning-tree portfast

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And let see if I did this right now

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so do sh int gigabit 0/2

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this port is now a Portfast port or what’s called an edge port, which is correct.

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do sh run g0/0 that shouldn’t be a Portfast port

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and it’s not and neither should gigabit 0/1 so that looks better.

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do sh spanning tree vlan 10

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notice the difference this is now a shared edge port, that looks a lot better.

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Let’s do the ping again at the moment gigabit 0/0 is the root port

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so int g0/0 shut the port down

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let’s see if we lose as many pings

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and as you’ve notice there we only lost a single ping.

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So I'll break that ping, we lost 1 ping

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we lost this last when I broke the ping

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but we only lost this single ping when the interface went down.

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So that’s a lot better than we had previously

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so do sh spanning-tree vlan 10

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notice gigabit 1/0 is the root port I'll send a 100 pings now

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and let's no shut the interface, let's make that a thousand

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sh spanning-tree vlan 10 what you’ll notice once again

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I dropped the single ping over there

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and it immediately revert it to port 1 being the root port.

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So what’s the moral of the story? These links need to be point-to-point links

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this link needs to be a Portfast port

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in other words, an edge port compares that to switch 4 on switch 4 this is a shared port.

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So it's gonna take longer for this to converge.

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On this switch we want to go into gigabit 0/2 and type spanning-tree portfast

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and now when we type sh spanning-tree vlan 20

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notice it's a shared edge port and we can do something similar now

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on router 2, I'll ping 10.1.20.1 and repeat that thousand times again.

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Go into gigabit 0/0 start the ping

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and I'll shut the port down notice we lost 1 ping.

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So do sh spanning tree  vlan 20 in this example

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forwarding port is now this port

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it’s the root port, this port is the edge port

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let’s do the ping again I'll no shut gigabit 0/0, now gigabit 0/0 is the root port

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and it’s already forwarding.

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The convergence is a lot better than we had previously

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we didn’t even lose a ping in this example.

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So let’s do that process again.

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Do a ping shut the port down, we’ve lost a ping but only 1

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I'll no shut the port, just too quick I'll shut it down again, do a ping again.

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Port to shut no shut it

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sh spanning-tree vlan

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do sh spanning tree vlan 10 or 20 in this example

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gigabit 0/0 is the root port gigabit 0/1 is the alternate port

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gigabit 0/2 is a shared edge port.

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So once again, to optimize Spanning Tree

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make all ports point-to-point links between your switches

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make your ports to your edge devices Spanning Tree Portsfast

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or edge ports as it's called in the industry.

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So Cisco term is Portfast other vendors will call these edge ports

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and we could do the same on these 2 ports here.

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So the last thing we need to do is on switch 1 go into gigabit 1/0

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and type spanning-tree portfast

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and then do the same on switch 2 int g1/0 spanning-tree portfast

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sh spanning-tree vlan 1 gigabit 1/0 is an edge port on switch 2

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sh spanning-tree vlan 1 on switch 1 notice this is an edge port here.

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So we’ve optimized Spanning Tree

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by making all of these ports point-to-point links in Spanning Tree.

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These ports are edge ports and these 2 ports are bonded in a link aggregation or Etherchannel.

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So once again, on switch 1 sh spanning-tree vlan 1

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notice this is a port channel and it's point-to-point link.

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Spanning Tree has been optimized, now that we’ve optimized layer 2

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we need to look at layer 3 functionality

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and specifically the default gateways of devices in the topology.

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We also need to think about routing

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how we're going to route from these devices into the Internet

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so we'll cover that in subsequent videos.