add STP toolkit Part 2 BPDU

2026-05-27 23:22:04 +02:00
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+---
+id: 1779884291-BCDN
+aliases:
+  - PortFast (STP Toolkit)
+tags: []
+---
+
+# PortFast (STP Toolkit)
+
+ex:
+Switch <-> PC
+
+Listening
+   | 15sec
+Learning
+   | 15sec
+Forwarding
+
+When an end host connects to a switch port, the port becomes up/up but can't send/receive data yet.
+- It is a *Designated port* but will take 30 seconds before it enters the Forwarding state:
+  - 15 seconds in Listening
+  - 15 seconds in Learning
+This lead to poor user experience
+- the user probably doesn't even know [[STP]] exists.
+- They just know "the internet doesn't work" for 30 seconds when they connect their computer.
+- This wait is unnecessary, because there is no risk of a Layer 2 loop occuring between a switch/PC
+
+## The solution
+
+When portFast is configured on a port, the port immediately enters the Forwardin state when connected 
+to another device.
+It bypasses Listening/Learning and can send/receive data right away
+
+You can configure PortFast in two ways
+
+1. Interface config mode
+
+```Cisco
+SW1(config-if)# spanning-tree portfast
+```
+
+This enables PortFast only on the individual interface.
+
+*Even if you configure spanning-tree porfast on a trunk port, it won't be active.*
+
+2. Global config mode:
+
+```Cisco
+SW1(config)# spanning-tree portfast default
+```
+
+This enables PorFast on all access ports.
+
+      Connections between switches are almost always trunk links.
+      Connections to end hosts are almost always access links.
+
+**PortFast should NOT be configured on ports connected to switches or temporary Layer 2
+loops can occur.**
+
+## showing result
+
+```Cisco
+SW1(config)# show spanning-tree interface g0/1 detail
+```
+
+## diabling portfast
+
+```Cisco
+SW1(config-if)# spanning-tree portfast disable
+```
+
+## Configurating Portfast on trunk port
+
+In some cases, you might want to enable PortFast on a trunk port:
+- A port connected to a virtualization server with virtual machines (VMs) in different VLANs.
+- A port connected to a [[router]] via router on a stick [[ROAS]].
+
+This can only be cofigured per-port in interface config mode:
+
+```Cisco
+SW1(config-if)# spanning tree portfast trunk
+```
+
+## PortFast Edge
+
+In modern Cisco switches, if you use the commands covered in this lecture, the device will automatically
+add the edge keyword to the configuration.
+
+```Cisco
+SW1(config-if)# spanning-tree portfast
+running-config
+spanning-tree portfast edge
+```
+
+```Cisco
+SW1(config-if)# spanning tree portfast trunk
+running-config
+spanning-tree portfast edge trunk
+```
+
+```Cisco
+SW1(config)# spanning-tree portfast default
+running-config
+spanning-tree portfast edge default
+```
+
+You can use either version of the commands when configuring PortFast.
+
+The end result is the same: edge will always be added in the configuraion.
+
+spanning-tree portfast disable doesn't use the *edge* keyword.
+
+
+## two kind of Portfast
+
+There are two kinds of PortFast:
+-  edge
+  - edge is the kind we are covering in this video
+-  network
+  - network is used for a feature called Bridge Assurance (not a CCNA topic)
+
+## Review
+
+### PortFast:
+Allows switchs ports connected to end hosts to immediately enter the STP Forwarding state.
+Bypassing Linstening and Learning