Product guide

Spanning-Tree Operation
802.1D Spanning-Tree Protocol (STP) on 5300xl, 3400cl and 6400cl Switches
Table 6-4. Per-Port STP Parameters
Name Default Range Function
path-cost Ethernet: 100
1 - 65535 Assigns an individual port cost that the switch uses
10/100Tx: 10
to determine which ports are the forwarding ports.
100 Fx: 10
Gigabit: 5
priority
mode
128
norm
0 - 255
norm
- or -
fast
- or -
uplink
Used by STP to determine the port(s) to use for
forwarding. The port with the lowest number has
the highest priority.
Specifies whether a port progresses through the
listening, learning, and forwarding (or blocking)
states (“norm” mode) or transitions directly to the
forwarding state (“fast” mode).
• For information on when to use Fast mode, see
“STP Fast Mode” on page 6-29.)
• For information on Uplink mode, see “Fast-
Uplink Spanning Tree Protocol (STP)” on
page 6-30
You can also include STP general parameters in this command. See “Recon-
figuring General STP Operation on the Switch” on page 6-27.
For example, the following configures ports C5 and C6 to a path cost of
15, a
priority of
100, and fast mode:
ProCurve(config)# spanning-tree c5-c6 path-cost 15 priority 100 mode fas
STP Fast Mode
For standard STP operation, when a network connection is established on a
device that is running STP, the port used for the connection goes through a
sequence of states (Listening and Learning) before getting to its final state
(Forwarding or Blocking, as determined by the STP negotiation). This
sequence takes two times the forward delay value configured for the switch.
The default is 15 seconds on ProCurve switches, per the IEEE 802.1D standard
recommendation, resulting in a total STP negotiation time of 30 seconds. Each
switch port goes through this start-up sequence whenever the network con-
nection is established on the port. This includes, for example, when the switch
or connected device is powered up, or the network cable is connected.
A problem can arise from this long STP start-up sequence because some end
nodes are configured to automatically try to access a network server when-
ever the end node detects a network connection. Typical server access
includes to Novell servers, DHCP servers, and X terminal servers. If the server
access is attempted during the time that the switch port is negotiating its STP
6-29