Cisco CCNP / BCMSN Exam Tutorial: Configuring PortFast And BPDU Guard
With your CCNA studies, you acquired about PortFast and The difficulty it may cause if configured 사설사이트 on the incorrect port! Suitable just for switch ports linked directly to just one host, PortFast enables a port running STP to go straight from blocking to forwarding manner.
A Cisco router gives you a warning any http://edition.cnn.com/search/?text=토토사이트 time you configure PortFast:
SW1(config)#int rapidly 0/5
SW1(config-if)#spanning-tree portfast
%Warning: portfast should only be enabled on ports linked to a
solitary host. Connecting hubs, concentrators, switches, bridges, and many others…
to this interface when portfast is enabled, can cause non permanent
bridging loops. Use with Warning
%Portfast has become configured on FastEthernet0/five but will only
have result when the interface is in a very non-trunking manner.
SW1(config-if)#
Not simply will the swap alert you about the right use of PortFast, but you need to put the port into access mode right before PortFast will choose influence.
Now, you’d feel that would be enough of the warning, correct? But there is a chance – just a chance – that someone is going to take care of to attach a switch into a port working Portfast. That could cause two important challenges, the very first getting the development of the switching loop. Keep in mind, The rationale We've listening and Mastering modes is to aid avoid switching loops. The next trouble is that there may be a completely new root bridge elected – and it may be a swap that isn’t even as part of your community!
BPDU Guard shields versus this disastrous possibility. If any BPDU comes in over a port that’s managing BPDU Guard, the port will be shut down and placed into error disabled condition, revealed on the change as err-disabled. A port placed in err-disabled state have to be reopened manually.
BPDU Guard is off on all ports by default, and it is enabled as revealed listed here:
SW1(config-if)#spanning-tree bpduguard empower
It’s a smart idea to enable BPDU Guard on any port you’re jogging PortFast on. There’s free of charge in overhead, and it does reduce the opportunity of a change sending BPDUs right into a port configured with PortFast – not to mention the possibility of a swap not beneath your Manage starting to be a root switch on your network!