Dell PowerConnect B-FCXs, Configuration Manual

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PowerConnect B-Series FCX Configuration Guide 209
53-1002266-01
Configuring standard STP parameters
8
NOTE
If you plan to change STP bridge timers, Dell recommends that you stay within the following ranges,
from section 8.10.2 of the IEEE STP specification.
2 * (forward_delay -1) >= max_age
max_age >= 2 * (hell1)
Table 49 lists the default STP port parameters. The port parameters affect individual ports and are
separately configurable on each port.
Enabling or disabling the Spanning Tree Protocol (STP)
STP is enabled by default on devices running Layer 2 code. STP is disabled by default on devices
running Layer 3 code.
You can enable or disable STP on the following levels:
•
Globally – Affects all ports and port-based VLANs on the device.
•
Port-based VLAN – Affects all ports within the specified port-based VLAN. When you enable or
disable STP within a port-based VLAN, the setting overrides the global setting. Thus, you can
enable STP for the ports within a port-based VLAN even when STP is globally disabled, or
disable the ports within a port-based VLAN when STP is globally enabled.
•
Individual port – Affects only the individual port. However, if you change the STP state of the
primary port in a trunk group, the change affects all ports in the trunk group.
Hello Time The interval of time between each configuration BPDU
sent by the root bridge. 2 seconds
Possible values: 1 – 10
seconds
Priority A parameter used to identify the root bridge in a spanning
tree (instance of STP). The bridge with the lowest value
has the highest priority and is the root.
A higher numerical value means a lower priority; thus, the
highest priority is 0. 32768
Possible values: 0 – 65535
TABLE 49
Default STP port parameters
Parameter Description Default and valid values
Priority The preference that STP gives this port relative to other
ports for forwarding traffic out of the spanning tree.
A higher numerical value means a lower priority. 128
Possible values: 0 – 240
(configurable in increments of
16)
Path Cost The cost of using the port to reach the root bridge. When
selecting among multiple links to the root bridge, STP
chooses the link with the lowest path cost and blocks the
other paths. Each port type has its own default STP path
cost. 10 Mbps – 100
100 Mbps – 19
Gbps – 4
10 Gbps – 2
Possible values are 0 – 65535
TABLE 48 Default STP bridge parameters (Continued)
Parameter Description Default and valid values