Cisco CCNP / BCMSN Test Tutorial: Configuring PortFast And BPDU Guard
Inside your CCNA reports, you discovered about PortFast and the trouble it could cause if configured on the incorrect port! Acceptable just for swap ports connected on to an individual host, PortFast makes it possible for a port running STP to go directly from blocking to forwarding manner.
A Cisco router will provide you with a warning whenever you configure PortFast:
SW1(config)#int fast 0/five
SW1(config-if)#spanning-tree portfast
%Warning: portfast really should only be enabled on ports linked to a
solitary host. Connecting hubs, concentrators, switches, bridges, and so on…
to this interface when portfast is enabled, could cause temporary
bridging loops. Use with Warning
%Portfast has been configured on FastEthernet0/5 but will only
have result in the event the interface is in a 메이저사이트 non-trunking mode.
SW1(config-if)#
Not merely will the change warn you about the correct use of PortFast, but it's essential to put the port into access method right before PortFast will take influence.
Now, you’d believe could well be ample of a warning, suitable? But there is an opportunity – just an opportunity – that someone is going to control to connect a swap to your port working Portfast. Which could bring on two significant difficulties, the very first getting the development of a switching loop. Don't forget, the reason We've got listening and Finding out modes is to aid reduce switching loops. Another issue is the fact there could possibly be a different root bridge elected – and it may be a switch http://www.thefreedictionary.com/토토사이트 that isn’t even inside your community!
BPDU Guard shields towards this disastrous likelihood. If any BPDU comes in with a port that’s operating BPDU Guard, the port will be shut down and placed into error disabled state, proven around the change as err-disabled. A port placed in err-disabled condition need to be reopened manually.
BPDU Guard is off on all ports by default, and it is enabled as proven in this article:
SW1(config-if)#spanning-tree bpduguard help
It’s a good idea to permit BPDU Guard on any port you’re managing PortFast on. There’s no cost in overhead, and it does protect against the potential of a switch sending BPDUs right into a port configured with PortFast – let alone the potential of a switch not below your Regulate becoming a root swap to your community!