Virtual Private LAN Services
7750 SR OS Services Guide Page 393
STP SAP Operational States
The operational state of STP within a SAP controls how BPDUs are transmitted and handled when
received. Defined states are:
• Operationally Disabled on page 393
• Operationally Discarding on page 393
• Operationally Learning on page 393
• Operationally Forwarding on page 394
Operationally Disabled
Operationally disabled is the normal operational state for STP on a SAP in a VPLS that has any of
the following conditions:
• VPLS state administratively down
• SAP state administratively down
• SAP state operationally down
If the SAP enters the operationally up state with the STP administratively up and the SAP STP
state is up, the SAP will transition to the STP SAP discarding state.
When, during normal operation, the router detects a downstream loop behind a SAP or spoke
SDP, BPDUs can be received at a very high rate. To recover from this situation, STP will
transition the SAP to disabled state for the configured forward-delay duration.
Operationally Discarding
A SAP in the discarding state only receives and sends BPDUs, building the local proper STP state
for each SAP while not forwarding actual user traffic. The duration of the discarding state is
explained in section Forward Delay on page 382.
Note: in previous versions of the STP standard, the discarding state was called a blocked state.
Operationally Learning
The learning state allows population of the MAC forwarding table before entering the forwarding
state. In this state, no user traffic is forwarded.
To Next Page
Loading...
