3Com 5500-SI Configuration Manual page 545

Table 595 RSTP Configuration (continued)
Device Configuration
Specify a Switch
as the root or
backup root
bridge
Configure the
Bridge
preference of a
Switch
Specify Forward
Delay, Hello
Time, and Max
Age
Specify the
maximum
transmission
rate of STP
packets on a
port
Configure
whether to
connect a port
with a
peer-to-peer link
Specify the Path
Cost on a port
Specify the
standard to
follow in Path
Cost calculation
Specify mCheck
for a port
Configure the
protection
functions on a
Switch
Switch C Enable the STP
and feature on the
Switch D Switch
Enable the STP
feature on the
port
Configure RSTP
operational
mode
Configure the
Bridge
preference of a
Switch
Default Value Note
The role of the A Switch can be made the root bridge by
current Switch as the specifying its Bridge preference to 0.
root or backup root
bridge depends on
the STP calculation.
The Bridge A Switch can be made the root bridge by
preference of a specifying its Bridge preference to 0.
Switch is 32768.
Forward Delay fixes The other Switches copies the
on 15 seconds, Hello configuration on the root bridge with
Times on 2 seconds, respect to these time parameters. You can
and Max Age on 20 therefore only configure them on the root
seconds. bridge. The default values are highly
recommended.
No Ethernet port can The more STP packets a port sends within
send more than 3 STP one Hello Time, the more resources are
packets within one consumed. It is therefore recommended to
Hello Time. limit the transmission rate of STP packets
on a port, preferably to the default value.
RSTP can detect The two ports connected with a
automatically peer-to-peer link can rapidly transit to the
whether the current forwarding status by sending synchronous
Ethernet port is packets, eliminating unnecessary
connect to a forwarding delay.
peer-to-peer link.
The Switch gets the The path cost of a port is closely related to
path cost of a port the transmission rate of the link the port
from the link rate connected with. The larger the link rate is,
under the IEEE 802.1t the smaller the path cost shall be. It is
standard. recommended to use the default
configuration.
- You can change the operational mode of a
port from STP-compatible to RSTP.
No protection It is recommended to enable the Root
function is enabled protection function on the root bridge.
on a Switch.
The STP feature is The configuration of STP feature status on
disabled from the the port will not take effect if the STP
Switch, but will be feature is disabled from the Switch.
enabled on all ports
once being enabled
on the Switch.
The Switch works in If there are Switches respectively running
RSTP mode. STP and RSTP on the network, it is
recommended to set the Switch in
STP-compatible mode.
The Bridge A Switch can be made the designated
preference of a bridge of the downstream Switches by
Switch is 32768. specifying an appropriate Bridge preference
in the STP calculation.
RSTP Configuration 545