Siemens RUGGEDCOM ROS v4.3 User Manual page 182

Chapter 5
Setup and Configuration
Parameter
Priority
STP Cost
RSTP Cost
Edge Port
Point to Point
166
Description
Enabling STP activates the STP or RSTP protocol for this port per
the configuration in the STP Configuration menu. STP may be
disabled for the port ONLY if the port does not attach to an STP
enabled bridge in any way. Failure to meet this requirement WILL
result in an undetectable traffic loop in the network. A better
alternative to disabling the port is to leave STP enabled but to
configure the port as an edge port. A good candidate for disabling
STP would be a port that services only a single host computer.
Synopsis: { 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176,
194, 208, 224, 240 }
Default: 128
Selects the STP port priority. Ports of the same cost that attach to
a common LAN will select the port to be used based upon the port
priority.
Synopsis: 0 to 65535 or { Auto }
Default: Auto
Selects the cost to use in cost calculations, when the Cost
Style parameter is set to STP in the Bridge RSTP Parameters
configuration. Setting the cost manually provides the ability to
preferentially select specific ports to carry traffic over others.
Leave this field set to "auto" to use the standard STP port costs as
negotiated (4 for 1Gbps, 19 for 100 Mbps links and 100 for 10
Mbps links).
For MSTP, this parameter applies to both external and internal
path cost.
Synopsis: 0 to 2147483647 or { Auto }
Default: Auto
Selects the cost to use in cost calculations, when the Cost
Style parameter is set to RSTP in the Bridge RSTP Parameters
configuration. Setting the cost manually provides the ability to
preferentially select specific ports to carry traffic over others.
Leave this field set to "auto" to use the standard RSTP port costs
as negotiated (20,000 for 1Gbps, 200,000 for 100 Mbps links and
2,000,000 for 10 Mbps links).
For MSTP, this parameter applies to both external and internal
path cost.
Synopsis: { False, True, Auto }
Default: Auto
Edge ports are ports that do not participate in the Spanning
Tree, but still send configuration messages. Edge ports transition
directly to frame forwarding without any listening and learning
delays. The MAC tables of Edge ports do not need to be flushed
when topology changes occur in the STP network. Unlike an STP
disabled port, accidentally connecting an edge port to another
port in the spanning tree will result in a detectable loop. The
"Edgeness" of the port will be switched off and the standard RSTP
rules will apply (until the next link outage).
Synopsis: { False, True, Auto }
Default: Auto
RSTP uses a peer-to-peer protocol that provides rapid transitioning
on point-to-point links. This protocol is automatically turned off in
situations where multiple STP bridges communicate over a shared
(non point-to-point) LAN. The bridge will automatically take point-
to-point to be true when the link is found to be operating in full-
duplex mode. The point-to-point parameter allows this behavior
or overrides it, forcing point-to-point to be true or false. Force the
parameter true when the port operates a point-to-point link but
Configuring STP for Specific Ethernet Ports
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