127 lines
3.1 KiB
Markdown
127 lines
3.1 KiB
Markdown
---
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id: 1779884291-BCDN
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aliases:
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- PortFast (STP Toolkit)
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tags: []
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---
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# PortFast (STP Toolkit)
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ex:
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Switch <-> PC
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Listening
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| 15sec
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Learning
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| 15sec
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Forwarding
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When an end host connects to a switch port, the port becomes up/up but can't send/receive data yet.
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- It is a *Designated port* but will take 30 seconds before it enters the Forwarding state:
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- 15 seconds in Listening
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- 15 seconds in Learning
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This lead to poor user experience
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- the user probably doesn't even know [[STP]] exists.
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- They just know "the internet doesn't work" for 30 seconds when they connect their computer.
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- This wait is unnecessary, because there is no risk of a Layer 2 loop occuring between a switch/PC
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## The solution
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When portFast is configured on a port, the port immediately enters the Forwardin state when connected
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to another device.
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It bypasses Listening/Learning and can send/receive data right away
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You can configure PortFast in two ways
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1. Interface config mode
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```Cisco
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SW1(config-if)# spanning-tree portfast
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```
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This enables PortFast only on the individual interface.
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*Even if you configure spanning-tree porfast on a trunk port, it won't be active.*
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2. Global config mode:
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```Cisco
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SW1(config)# spanning-tree portfast default
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```
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This enables PorFast on all access ports.
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Connections between switches are almost always trunk links.
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Connections to end hosts are almost always access links.
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**PortFast should NOT be configured on ports connected to switches or temporary Layer 2
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loops can occur.**
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## showing result
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```Cisco
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SW1(config)# show spanning-tree interface g0/1 detail
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```
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## diabling portfast
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```Cisco
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SW1(config-if)# spanning-tree portfast disable
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```
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## Configurating Portfast on trunk port
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In some cases, you might want to enable PortFast on a trunk port:
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- A port connected to a virtualization server with virtual machines (VMs) in different VLANs.
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- A port connected to a [[router]] via router on a stick [[ROAS]].
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This can only be cofigured per-port in interface config mode:
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```Cisco
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SW1(config-if)# spanning tree portfast trunk
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```
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## PortFast Edge
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In modern Cisco switches, if you use the commands covered in this lecture, the device will automatically
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add the edge keyword to the configuration.
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```Cisco
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SW1(config-if)# spanning-tree portfast
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running-config
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spanning-tree portfast edge
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```
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```Cisco
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SW1(config-if)# spanning tree portfast trunk
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running-config
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spanning-tree portfast edge trunk
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```
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```Cisco
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SW1(config)# spanning-tree portfast default
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running-config
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spanning-tree portfast edge default
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```
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You can use either version of the commands when configuring PortFast.
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The end result is the same: edge will always be added in the configuraion.
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spanning-tree portfast disable doesn't use the *edge* keyword.
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## two kind of Portfast
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There are two kinds of PortFast:
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- edge
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- edge is the kind we are covering in this video
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- network
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- network is used for a feature called Bridge Assurance (not a CCNA topic)
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## Review
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### PortFast:
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Allows switchs ports connected to end hosts to immediately enter the STP Forwarding state.
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Bypassing Linstening and Learning
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