Cisco CCNP / BCMSN Exam Tutorial: Configuring PortFast And BPDU Guard
Inside your CCNA research, you uncovered about PortFast and The difficulty it may cause if configured on the wrong port! Acceptable just for switch ports related directly to only one host, PortFast enables a port managing STP to go straight from blocking to forwarding manner.
A Cisco router offers you a warning when you configure PortFast:
SW1(config)#int rapidly 0/5
SW1(config-if)#spanning-tree portfast
%Warning: portfast ought to only be enabled on ports linked to a
single host. Connecting hubs, concentrators, switches, bridges, etc…
to this interface when portfast is enabled, can result in short term
bridging loops. Use with Warning
%Portfast is configured on FastEthernet0/five but will only
have outcome in the event the interface is within a non-trunking mode.
SW1(config-if)#
Not merely will the swap alert you about the right use of PortFast, but you need to put the port into obtain mode before PortFast will choose impact.
Now, you’d imagine that might be sufficient of a warning, appropriate? But there is a chance – just an opportunity – that someone will probably deal with to attach a change to some port jogging Portfast. That may cause two important difficulties, the main staying the development of the switching loop. Don't forget, The main reason We've listening and learning modes is to help you avoid switching loops. The following issue is always that there could possibly be a different root bridge elected – and it may be a swap that isn’t even as part of your network!
BPDU Guard protects in opposition to this disastrous probability. If any BPDU is available in with a port that’s jogging BPDU Guard, the port will likely be shut down and put into error disabled condition, demonstrated over the switch as err-disabled. A port placed in err-disabled point out needs to be reopened manually.
BPDU Guard is off on all ports by default, and https://en.wikipedia.org/wiki/?search=토토사이트 is also enabled as demonstrated here:
SW1(config-if)#spanning-tree bpduguard permit
It’s a smart idea to allow BPDU Guard on any port you’re operating PortFast on. There’s free of charge in overhead, and it does avoid the opportunity of a change sending 먹튀검증사이트 BPDUs right into a port configured with PortFast – not forgetting the opportunity of a change not less than your Handle turning into a root swap towards your network!