Spanning-Tree Operation
802.1D Spanning-Tree Protocol (STP)
Caution 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
Note 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:
• STP is running on both switches.
• Port “A” and port “B” are both configured for
fast-uplink STP (Mode = Uplink).
STP Root
Switch
2610, 2610-
PWR,
(Wiring
Closet or
Edge
Switch)
LAN
STP Blocking
Port A is the STP root port.
B
Port B provides a backup redundant link.
that becomes the new STP root port
(uplink port) if the link through port A
C
A
D
E
Figure 5-12. Example of How To Implement Fast-Uplink STP
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