Virtual Private LAN Services
7750 SR OS Services Guide Page 395
Each SAP has a Read Only operational state that shows which BPDU encapsulation is currently
active on the SAP. The following states apply:
• Dot1d specifies that the switch is currently sending IEEE 802.1d standard BPDUs. The
BPDUs will be tagged or non-tagged based on the encapsulation type of the egress
interface and the encapsulation value defined in the SAP. A SAP defined on an interface
with encapsulation type dot1q will continue in the dot1d BPDU encapsulation state until a
PVST encapsulated BPDU is received, in which case the SAP will convert to the PVST
encapsulation state. Each received BPDU must be properly IEEE 802.1q tagged if the
interface encapsulation type is defined as dot1q. PVST BPDUs will be silently discarded
if received when the SAP is on an interface defined with encapsulation type null.
• PVST specifies that the switch is currently sending proprietary encapsulated BPDUs.
PVST BPDUs are only supported on Ethernet interfaces with the encapsulation type set to
dot1q. The SAP continues in the PVST BPDU encapsulation state until a dot1d
encapsulated BPDU is received, in which case the SAP reverts to the dot1d encapsulation
state. Each received BPDU must be properly IEEE 802.1q tagged with the encapsulation
value defined for the SAP. PVST BPDUs are silently discarded if received when the SAP
is on an interface defined with a null encapsulation type.
Dot1d is the initial and only SAP BPDU encapsulation state for SAPs defined on Ethernet
interface with encapsulation type set to null.
Each transition between encapsulation types optionally generates an alarm that can be logged and
optionally transmitted as an SNMP trap.
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