144BigIron RX Series Configuration Guide53-1001986-01Port transition hold timer6Port transition hold timerUsing the delay-link-event command will delay the sending of port "up" or "down" events to Layer 2protocols. While link down events are reported immediately in syslog, their effect on higher levelprotocols such as OSPF is delayed according to how the delay-link-event is configured. Thiscommand affects the physical link events. However, the resulting logical link events are alsodelayed. This is a per-interface command.For example, if VSRP is enabled on the port, the ownership would not change until the port statushas remained up or down for the configured amount of time to ensure that minor transient statesof a link do not unintentionally cause a disruptive topology change in the network.NOTEAll trunk ports must have the same delayed-link-down-event configuration.The following command will delay the sending of port "down" event for 100ms when a port state isdetected "down". If the port state is detected "up" afterwards within 100ms, the delayed "down"event is cancelled; otherwise, the "down" event is sent after 100ms. This allows the upper layerapplications not to be affected by a port state flapping.BigIronRX(config-if-e1000-1/2)#delay-link-event2downSyntax: delay-link-event The The parameter means only "up" events are delayed.The parameter means that only the down events are delayed.Port flap dampeningThe port flap dampening feature allows you to configure a wait period before a port, whose linkgoes down then up, becomes enabled.If the port flap state toggles (from down to up or from up to down) for a specified number of timeswithin a specified period, the interface is physically disabled for the specified wait period. Once thewait period expires, the port’s link state is re-enabled. However, if the wait period is set to zero (0)seconds, the port’s link state will remain disabled until it is manually re-enabled.Configuration notes•When a link dampening port becomes a member of a trunk group, that port, as well as all othermember ports of that trunk group, will inherit the primary port’s configuration. This meansthat the member ports will inherit the primary port’s link dampening configuration, regardlessof any previous configuration.•TheBrocadedevice counts the number of times a port’s link state toggles from "up to down",and not from "down to up".•The sampling time or window (the time during which the specified toggle threshold can occurbefore the wait period is activated) is triggered when the first "up to down" transition occurs.•"Up to down" transitions include UDLD-based toggles, as well as the physical link state.
