FD 100/320Gbps NT and FX NT IHub Services Guide Virtual Private LAN Service
Issue: 13 3HH-11985-AAAA-TQZZA 213
5.8.6.1 Operationally Disabled
Operationally disabled is the normal operational state for STP on an 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 an
SAP, 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.
5.8.6.2 Operationally Discarding
An 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 “forward-delay”.
5.8.6.3 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.
5.8.6.4 Operationally Forwarding
Configuration BPDUs are sent out an SAP in the forwarding state. Layer 2 frames
received on the SAP are source learned and destination forwarded according to the
FIB. Layer 2 frames received on other forwarding interfaces and destined for the SAP
are also forwarded.
Note — In previous versions of the STP standard, the
discarding state was called a blocked state.
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