Spanning Tree Protocol and PortFast

What is Spanning Tree and Portfast, and how can they affect my Altiris environment?

During the execution of the Spanning-Tree Algorithm, Spanning-Tree will force the ports to go into five different states:

Blocked
Listen
Learn
Forward
Disabled

The transitioning period from state to state takes the following times by default:

From blocking to listening: 20 seconds
From listening to learning: 15 seconds
From learning to forwarding: 15 seconds

PortFast causes a port to enter the forwarding state almost immediately by dramatically decreasing the time of the listening and learning states. Portfast minimizes the time it takes for the server or workstation to come online, thus preventing problems with applications such as DHCP, DNS, Novell IPX, PXE, BootWorks, etc.

PortFast causes a switch or trunk port to enter the spanning tree forwarding state immediately, bypassing the listening and learning states.

You can use PortFast on switch or trunk ports that are connected to a single workstation, switch, or server to allow those devices to connect to the network immediately, instead of waiting for the port to transition from the listening and learning states to the forwarding state.

When the switch powers up, or when a device is connected to a port, the port enters the spanning tree listening state. When the Forward Delay timer expires, the port enters the learning state. When the Forward Delay timer expires a second time, the port is transitioned to the forwarding or blocking state.

When you enable PortFast on a switch or trunk port, the port is immediately transitioned to the spanning tree forwarding state.

Reference:

https://support.symantec.com/en_US/article.HOWTO6019.html
What is Spanning Tree and Portfast, and how can they affect my Altiris environment?

http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/5234-5.html
Understanding and Configuring Spanning Tree Protocol (STP) on Catalyst Switches

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4000/8-2glx/configuration/guide/stp_enha.html
Configuring Spanning Tree PortFast, BPDU Guard, BPDU Filter, UplinkFast, BackboneFast, and Loop Guard

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