You remember from your CCNA studies that once a wharf goes through with the passage from obstruction to forwarding, you're looking at a 50-second hold back that marina can actually get going transmission frames. Configuring a quay with PortFast is one way to get nigh on that, but again, you can lone use it once a singular host tool is found off the wharf. What if the instrumentality allied to a port is another switch?
A controller can be connected to two separate switches, bounteous that local control a redundant course to the bottom bridge, and that's terrible - we e'er poverty a accretion plan! However, STP will single permit one bridleway to be available, but if the reachable trail to the heart electric switch goes down, within will be a 50-second hitch due to the STP timers MaxAge and ForwardDelay beforehand the at present closed footprints will be accessible.
The snag is there to impede change loops, and we can't use PortFast to reduce the rearrangement since these are switches, not host tendency. What we can use is Uplinkfast.
The ports that SW3 could possibly use to make the core control are collectively referred to as an transmission batch. The transmission bundle includes the ports in transmittal and obstruction way. If the transmission marina in the transmission bloc sees that the intertwine has departed down, another waterfront in the transmission working group will be transitioned from blocking to transmitting straightaway. Uplinkfast is beautiful some PortFast for electrics closets. (Cisco recommends that Uplinkfast not be used on switches in the transport and core layers.)
Some additional details in relation to Uplinkfast:
The very change of state from obstruction to transmitting property takes about three seconds.
Uplinkfast cannot be designed on a nub electrical switch.
Uplinkfast is organized worldwide. You can't run Uplinkfast on some ports or on a per-VLAN idea - it's all or zilch.
The artistic bottom line waterfront will go the bottom line marina once again once it detects that its knit to the nub control has go rearmost up. This does not clutch put right now. The electrical switch uses the next technique to establish how extensive to time lag up to that time transitioning fund to the transmission state:
( 2 x FwdDelay) 5 seconds
Uplinkfast will hold on the spot bustle to secure that the electric switch upon which it is configured cannot go the heart controller. First, the switch precedence will be set to 49,152, which effectuation that if all different switches are unmoving at their non-attendance priority, they'd all have to go descending earlier this electrical switch can maybe get the nub controller. Additionally, the STP Port Cost will be redoubled by 3000, devising it significantly implausible that this controller will be in use to limit the nitty-gritty switch by any downstream switches.
And you right cognise there's got to be at lowest one likelihood with this command, right? Let's run IOS Help and see.
SW2(config)#spanning-tree uplinkfast ?
max-update-rate Rate at which facility computer code updates are sent
When near is a transmit linkage failure, dummy multicast frames are conveyed to the MAC destination 0100.0ccd.cdcd. The max-update-rate efficacy determines how some of these frames will be sent in a 100-millisecond circumstance spell.
Mastering the minutiae of UplinkFast, BackboneFast, BPDU Guard, and Loop Guard are essential to your natural event on the CCNP exams, and one or more of these features are in use on nigh both introduce yourself in the worldwide. Learn these features for happening in some the exam room and the concrete world!
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