Chapter 7
| Spanning Tree Algorithm
Configuring Interface Settings for STA
– 218 –
Parameters
These parameters are displayed:
◆ Interface – Displays a list of ports or trunks.
◆ Spanning Tree – Enables/disables STA on this interface. (Default: Enabled)
◆ BPDU Flooding - Enables/disables the flooding of BPDUs to other ports when
global spanning tree is disabled (page 211) or when spanning tree is disabled
on a specific port. When flooding is enabled, BPDUs are flooded to all other
ports on the switch or to all other ports within the receiving port’s native VLAN
as specified by the Spanning Tree BPDU Flooding attribute (page 211).
(Default: Enabled)
◆ Priority – Defines the priority used for this port in the Spanning Tree Protocol.
If the path cost for all ports on a switch are the same, the port with the highest
priority (i.e., lowest value) will be configured as an active link in the Spanning
Tree. This makes a port with higher priority less likely to be blocked if the
Spanning Tree Protocol is detecting network loops. Where more than one port
is assigned the highest priority, the port with lowest numeric identifier will be
enabled.
■
Default: 128
■
Range: 0-240, in steps of 16
◆ Admin Path Cost – This parameter is used by the STA to determine the best
path between devices. Therefore, lower values should be assigned to ports
attached to faster media, and higher values assigned to ports with slower
media. Note that path cost takes precedence over port priority. (Range: 0 for
auto-configuration, 1-65535 for the short path cost method
6
, 1-200,000,000 for
the long path cost method)
By default, the system automatically detects the speed and duplex mode used
on each port, and configures the path cost according to the values shown
below. Path cost “0” is used to indicate auto-configuration mode. When the
short path cost method is selected and the default path cost recommended by
the IEEE 8021w standard exceeds 65,535, the default is set to 65,535.
6. Refer to “Configuring Global Settings for STA” on page 211 for information on setting the
path cost method.
Table 10: Recommended STA Path Cost Range
Port Type IEEE 802.1D-1998 IEEE 802.1w-2001
Ethernet 50-600 200,000-20,000,000
Fast Ethernet 10-60 20,000-2,000,000
Gigabit Ethernet 3-10 2,000-200,000
10G Ethernet 1-5 200-20,000
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