Spanning-Tree Operation

802.1D Spanning-Tree Protocol (STP)

C a u t i o n

N o t e

In general, fast-uplink spanning tree on the switch is useful when running STP in a tiered topology that has well-defined edge switches. Also, ensure that an interior switch is used for the root switch and for any logical backup root switches. You can accomplish this by using the Spanning Tree Priority (some­ times termed bridge priority) settings that define the primary STP root switch and at least one failover root switch (in the event that the primary root switch fails). Inappropriate use of Fast-Uplink STP can cause intermittent loops in a network topology. For this reason, the Fast-Uplink STP feature should be used only by experienced network administrators who have a strong understanding of the IEEE 802.1D standard and STP interactions and operation. If you want to learn more about STP operation, you may find it helpful to refer to publications such as:

Perlman, Radia, Interconnections: Bridges, Routers, Switches, and Internetworking Protocols (second edition), Addison-Wesley Profes­ sional Computing Series, October 1999

When properly implemented, fast-uplink STP offers a method for achieving faster failover times than standard STP, and is intended for this purpose for instances where 802.1D STP has been chosen over 802.1w RSTP.

To use fast-uplink STP, configure fast-uplink (Mode = Uplink) only on the switch’s upstream ports; (that is, two or more ports forming a group of redundant links in the direction of the STP root switch). If the active link in this group goes down, fast-uplink STP selects a different upstream port as the root port and resumes moving traffic in as little as ten seconds. The device(s) on the other end of the links must be running STP. However, because fast uplink should be configured only on the switch’s uplink ports, the device(s) on the other end of the links can be either ProCurve devices or another vendor’s devices, regardless of whether they support fast uplink. For example:

 

 

 

 

 

 

 

 

 

 

 

Port A is the STP root port.

 

 

 

 

 

 

 

 

 

 

C

2610, 2610­

 

 

A

 

 

D

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PWR,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Wiring

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Closet or

 

B

 

E

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edge

 

 

 

 

 

 

 

 

 

 

 

 

 

Switch)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Port B provides a backup redundant link.

 

STP Blocking

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

that becomes the new STP root port

 

 

 

 

 

 

 

 

 

 

 

 

 

(uplink port) if the link through port A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

STP Root

Switch

LAN

•STP is running on both switches.

•Port “A” and port “B” are both configured for fast-uplink STP (Mode = Uplink).

Figure 5-12. Example of How To Implement Fast-Uplink STP

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