Cisco CCNP / BCMSN Exam Tutorial: Configuring PortFast And BPDU Guard
Within your CCNA studies, you uncovered about PortFast and The difficulty it might cause if configured on the incorrect port! Acceptable just for swap ports linked straight to just one host, PortFast lets a port jogging STP to go directly from blocking to forwarding method.
A Cisco router provides you with a warning whenever you configure PortFast:
SW1(config)#int quick 0/5
SW1(config-if)#spanning-tree portfast
%Warning: portfast should really only be enabled on ports linked to a
one host. Connecting hubs, concentrators, switches, bridges, and 안전놀이터 so forth…
to this interface when portfast is enabled, might cause temporary
bridging loops. Use with CAUTION
%Portfast has become configured on FastEthernet0/5 but will only
have influence when the interface is in the non-trunking mode.
SW1(config-if)#
Not only will the change warn you about the appropriate utilization of PortFast, but you will need to put the port into obtain manner just before PortFast will choose impact.
Now, you’d feel that could be sufficient of a warning, proper? But there's an opportunity – just an opportunity – that someone is going to deal with to connect a switch to some port managing Portfast. That may result in two main problems, the initial becoming the formation of the switching loop. Bear in mind, The key reason why We've got listening and learning modes is to aid reduce switching loops. The subsequent problem is there may very well be a brand new root bridge elected – and it could be a swap that isn’t even in your network!
BPDU Guard guards against this disastrous chance. If any BPDU is available in on a port that’s functioning BPDU Guard, the port are http://www.bbc.co.uk/search?q=토토사이트 going to be shut down and placed into mistake disabled state, shown on the change as err-disabled. A port placed in err-disabled condition has to be reopened manually.
BPDU Guard is off on all ports by default, and is particularly enabled as shown below:
SW1(config-if)#spanning-tree bpduguard help
It’s a good idea to help BPDU Guard on any port you’re managing PortFast on. There’s no cost in overhead, and it does reduce the potential for a switch sending BPDUs into a port configured with PortFast – not forgetting the possibility of a swap not beneath your control turning into a root change to your network!