FD 100/320Gbps NT and FX NT IHub Services Guide Virtual Private LAN ServiceIssue: 13 3HH-11985-AAAA-TQZZA 2855.16.3.4 forward-delayTable 186 forward-delay commandContext configure>service>vpls>sap>stpDescription This command configures the SAP as an edge or non-edge port. If auto-edge is enabled forthe SAP, this value will be used only as the initial value.Note: The function of the edge-port command is similar to the rapid-start command. It tellsRSTP that it is on the edge of the network (for example, there are no other bridges connectedto that port) and, as a consequence, it can immediately transition to a forwarding state if theport becomes available.RSTP, however, can detect that the actual situation is different from what edge-port mayindicate.Initially, the value of SAP parameter is set to edge-port. This value will change if:• A BPDU is received on that port. This means that after all there is another bridge connectedto this port. Then the edge-port becomes disabled.• If auto-edge is configured and no BPDU is received within a certain period of time, RSTPconcludes that it is on an edge and enables the SAP edge-port.The no form of this command returns the edge port setting to the default value.Default no edge-portItem Description(2 of 2)Item DescriptionSyntax forward-delay secondsno forward-delayContext configure>service>vpls>stpDescription RSTP, as defined in the IEEE 802.1D-2004 standards, will normally transition to the forwardingstate via a handshaking mechanism (rapid transition), without any waiting times. Ifhandshaking fails (e.g. on shared links, see below), the system falls back to the timer-basedmechanism defined in the original STP (802.1D-1998) standard.A shared link is a link with more than two nodes (for example, a shared 10/100BaseTsegment). The port-type command is used to configure a link as point-to-point or shared.For timer-based transitions, the 802.1D-2004 standard defines an internal variableforward-delay, which is used in calculating the default number of seconds that an SAP spendsin the discarding and learning states when transitioning to the forwarding state.The value of the forward-delay variable depends on the STP operating mode of the VPLSinstance:• In RSTP or MSTP mode, but only when the SAP has not fallen back to legacy STPoperation, the value configured by the hello-time command is used.• In all other situations, the value configured by the forward-delay command is used.Default 15Parameters seconds — The forward delay timer for the STP instance in seconds.Values: 4 — 30
