NAME
stp - Spanning Tree Protocol
SYNOPSIS
DESCRIPTION
Spanning Tree (STP) is a layer 2 protocol designed to run on bridges. The
main purpose of STP is to ensure that there are no loop situations when
redundant paths are provisioned in the network. STP detects and disables
creation of network loops by blocking certain ports on some of the bridges
in the network. The process of selection of blocking ports (on occurance
of redundant paths) is governed by the following three parameters :
- Relative priority of each bridge. A higher value means lower priority.
- Relative priority of each port within a bridge. A higher value means
lower priority.
- Path cost (based on physical media type) associated with each port.
A given port/interface participates in STP if the flag IFBIF_STP is
set for the interface. A possible time for setting this flag is at the
time when the interface in context is added to bridge.
IOCTLS
The STP code is invoked for all ioctl calls specified in bridge section.
The following ioctl calls are specific to STP functionality. They are
defined in <sys/sockio.h>.
SIOCBRDGGPRI (struct ifbrparam) Get the configured priority of this
bridge. The priority value could vary from 0 to 65535.
0 being the highest priority and 65535 the lowest. The
configured value is returned in field ifbrp_prio.
SIOCBRDGSPRI (struct ifbrparam) Set priority of this bridge to the
value specified in field ifbrp_prio.
SIOCBRDGGHT (struct ifbrparam) Get the configured frequency of
transmission of hello packets from non-blocking
interfaces on this bridge. The configured frequency is
returned in field ifbrp_hellotime.
SIOCBRDGSHT (struct ifbrparam) Set the frequency of transmission
of hello packets to the value specified in field
ifbrp_hellotime. The specified value should be greater
than 0, else EINVAL is returned.
SIOCBRDGGFD (struct ifbrparam) Get the forwarding delay time
associated with ports/interfaces on this bridge. The
forwarding delay time is the time taken by a port
to transit from one state to other (for eg. from
LEARNING state to FORWARDING state). The configured
value if returned in field ifbrp_fwddelay.
SIOCBRDGSFD (struct ifbrparam) Set the forwarding delay for ports
attached to this bridge to a value specified in
field ifbrp_fwddelay. The specified value should be
greater than 0, else EINVAL is returned.
SIOCBRDGGMA (struct ifbrparam) Get aging timeout values of
spanning data. The timeout value is returned in field
ifbrp_maxage.
SIOCBRDGSMA (struct ifbrparam) Set the aging timeout value of
BPDUs to the value specified in ifbrp_maxage. The
specified value should be greater than 0, else
EINVAL is returned.
SIOCBRDGSIFPRIO (struct ifbreq) Set the priority of specified
interface to the value given in field ifbr_priority.
SIOCBRDGSIFCOST (struct ifbreq) Set the cost associated with the
given interface to the value specified in field
ifbr_path_cost.
ERRORS
Same as the ones specified for bridge.
SEE ALSO
netintro, bridge
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