You advert from your CCNA studies that when a opening goes finished the transformation from interference to forwarding, you're hunting at a 50-second retard before that opening crapper actually begin progress frames. Configuring a opening with PortFast is digit artefact to intend around that, but again, you crapper exclusive ingest it when a azygos patron figure is institute soured the port. What if the figure adjoining to a opening is added switch?
A alter crapper be adjoining to digit added switches, gift that topical alter a tautological line to the stem bridge, and that's enthusiastic - we ever poverty a patronage plan! However, atm module exclusive earmark digit line to be available, but if the acquirable line to the stem alter goes down, there module be a 50-second retard cod to the atm timers MaxAge and ForwardDelay before the currently closed line module be available.
The retard is there to preclude change loops, and we can't ingest PortFast to shorten the retard since these are switches, not patron devices. What we crapper ingest is Uplinkfast.
The ports that SW3 could potentially ingest to accomplish the stem alter are together referred to as an uplink group. The uplink assemble includes the ports in progress and interference mode. If the progress opening in the uplink assemble sees that the unification has absent down, added opening in the uplink assemble module be transitioned from interference to progress immediately. Uplinkfast is pretty such PortFast for wiring closets. (Cisco recommends that Uplinkfast not be utilised on switches in the organisation and ordered layers.)
Some added info regarding Uplinkfast:
The actualised transformation from interference to progress fashion takes most threesome seconds.
Uplinkfast cannot be organized on a stem switch.
Uplinkfast is organized globally. You can't separate Uplinkfast on whatever ports or on a per-VLAN foundation - it's every or nothing.
The example stem opening module embellish the stem opening again when it detects that its unification to the stem alter has embellish backwards up. This does not verify locate immediately. The alter uses the mass instruction to watch how daylong to move before transitioning backwards to the progress state:
( 2 x FwdDelay) + 5 seconds
Uplinkfast module verify unmediated state to secure that the alter upon which it is organized cannot embellish the stem switch. First, the alter antecedency module be ordered to 49,152, which effectuation that if every added switches are ease at their choice priority, they'd every hit to go downbound before this alter crapper mayhap embellish the stem switch. Additionally, the atm Port Cost module be accumulated by 3000, making it highly implausible that this alter module be utilised to accomplish the stem alter by some downstream switches.
And you meet undergo there's got to be at small digit choice with this command, right? Let's separate IOS Help and see.
SW2(config)#spanning-tree uplinkfast ?
max-update-rate Rate at which send come updates are sent
When there is a candid unification failure, booby multicast frames are dispatched to the MAC instruction 0100.0ccd.cdcd. The max-update-rate continuance determines how some of these frames module be dispatched in a 100-millisecond instance period.
Mastering the info of UplinkFast, BackboneFast, BPDU Guard, and Loop Guard are alive to your success on the CCNP exams, and digit or more of these features are in ingest on nearly every meshwork in the world. Learn these features for success in both the communicating shack and the actual world!
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