Cisco CCNP / BCMSN Examination Tutorial: Configuring PortFast And BPDU Guard
In your CCNA experiments, you uncovered about PortFast and The difficulty it could cause if configured on the incorrect port! Appropriate only for swap ports linked directly to only one host, PortFast will allow a port managing STP to go directly from blocking to forwarding manner.
A Cisco router provides you with a warning any http://edition.cnn.com/search/?text=토토사이트 time you configure PortFast:
SW1(config)#int speedy 0/5
SW1(config-if)#spanning-tree portfast
%Warning: portfast should really only be enabled on ports connected to a
one host. Connecting hubs, concentrators, switches, bridges, and so on…
to this interface when portfast is enabled, may cause short-term
bridging loops. Use with Warning
%Portfast has been configured on FastEthernet0/5 but will only
have outcome once the interface is inside of a non-trunking method.
SW1(config-if)#
Don't just will the swap alert you about the appropriate use of PortFast, but you need to place the port into accessibility manner before PortFast will take result.
Now, you’d think that would be enough of the warning, ideal? But there's a chance – just an opportunity – that someone will take care of to attach a switch to your port running Portfast. That may result in two main complications, the main being the formation of a switching loop. Recall, the reason We have now listening and Mastering modes is to assist avoid switching loops. The subsequent problem 안전공원 is the fact that there can be a different root bridge elected – and it could be a switch that isn’t even within your network!
BPDU Guard protects towards this disastrous possibility. If any BPDU comes in on the port that’s working BPDU Guard, the port will probably be shut down and put into mistake disabled state, proven around the switch as err-disabled. A port positioned in err-disabled state must be reopened manually.
BPDU Guard is off on all ports by default, and it is enabled as demonstrated in this article:
SW1(config-if)#spanning-tree bpduguard permit
It’s a good idea to enable BPDU Guard on any port you’re functioning PortFast on. There’s no cost in overhead, and it does stop the potential for a change sending BPDUs into a port configured with PortFast – not to mention the potential for a change not underneath your Regulate getting a root switch to the community!