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CHAPTER 13: RAPID SPANNING TREE PROTOCOL RAPID SPANNING TREE PROTOCOL
MULTILINK ML1200 MANAGED FIELD SWITCH – INSTRUCTION MANUAL 13–7
• Path Cost: This is the assigned port cost value used for the switch to determine the
forwarding points. Values range from 1 to 2000000. Lower values indicate a lower
cost and hence the preferred route. The costs for different Ethernet speeds are
indicated below. The Path cost in STP is compared to the path cost in RSTP.
• State: Indicates the STP state of individual ports. Values can be Listening, Learning,
Forwarding, Blocking and Disabled.
• Des. Bridge: This is the port's designated root bridge
• Des. Port: This is the port's designated root port
Another example of the same command, from a larger network with several switches is
shown in Example 13-3. Note the
show stp ports command can be executed from the
manager level prompt or from RSTP configuration state as shown in the screen captures
earlier
In this example, ports 9 and 10 have a path cost of 20000 and are the least cost paths.
These ports are connected to other switches and the ports are enabled as forwarding
ports. Ports 6 and 7 are also connected to other switches. From the state column, it
indicates that port 7 is in a standby state as that port is discarding all traffic.
More CLI commands associated with RSTP in the RSTP configuration mode are shown
below. The
forceversion command sets the STP or RSTP compatibility mode.
forceversion <stp|rstp>
The
show-forceversion command displays the current forced version.
show-forceversion
Table 13–1: Path cost as defined in IEEE 802.1d / 802.1w
Port type STP path cost RSTP path cost
10 Mbps 100 2000000
100 Mbps 19 200000
1 Gbps 4 20000
10 Gbps 2 2000
Example 13-3: RSTP information from a network with multiple switches
ML1200(rstp)##show stp ports
RSTP Port Configuration
-------------------------------------------------------------------------------
Port# Type Priority Path Cost State Des. Bridge Des. Port
-------------------------------------------------------------------------------
01 TP(10/100) 128 200000 Forwarding 80:00:00:20:06:30:00:01 00:01
02 TP(10/100) 128 2000000 Disabled 00:02
03 100MB Fiber 128 200000 Disabled 00:03
04 100MB Fiber 128 200000 Disabled 00:04
05 100MB Fiber 128 200000 Disabled 00:05