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.
Table 5: Recommended STA Path Cost Range
Port Type
Ethernet
Fast Ethernet
Gigabit Ethernet
Table 6: Recommended STA Path Costs
Port Type
Link Type
Ethernet
Half Duplex
Full Duplex
Trunk
Fast Ethernet
Half Duplex
Full Duplex
Trunk
Gigabit Ethernet
Full Duplex
Trunk
Table 7: Default STA Path Costs
Port Type
Ethernet
Fast Ethernet
Gigabit Ethernet
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.
(Range: 0-240, in steps of 16; Default: 128)
Admin Edge (Fast Forwarding) – You can enable this option if an
◆
interface is attached to a LAN segment that is at the end of a bridged
LAN or to an end node. Since end nodes cannot cause forwarding loops,
they can pass directly through to the spanning tree forwarding state.
Specifying edge ports provides quicker convergence for devices such as
workstations or servers, retains the current forwarding database to
reduce the amount of frame flooding required to rebuild address tables
– 79 –
C
HAPTER
Configuring the Spanning Tree Algorithm
IEEE 802.1D-1998
50-600
10-60
3-10
IEEE 802.1D-1998
100
95
90
19
18
15
4
3
Link Type
Half Duplex
Full Duplex
Trunk
Half Duplex
Full Duplex
Trunk
Full Duplex
Trunk
| Configuring the Switch
4
IEEE 802.1w-2001
200,000-20,000,000
20,000-2,000,000
2,000-200,000
IEEE 802.1w-2001
2,000,000
1,999,999
1,000,000
200,000
100,000
50,000
10,000
5,000
IEEE 802.1w-2001
2,000,000
1,000,000
500,000
200,000
100,000
50,000
10,000
5,000