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