Cisco CCNP / BCMSN Exam Tutorial: Configuring PortFast And BPDU Guard
In your CCNA reports, you realized about PortFast and the trouble it might cause if configured on the wrong port! Appropriate only for switch ports linked straight to only one host, PortFast enables a port functioning STP to go directly from blocking to forwarding manner.
A Cisco router gives you a warning after you configure PortFast:
SW1(config)#int rapidly 0/five
SW1(config-if)#spanning-tree portfast
%Warning: portfast need to only be enabled on ports connected to a
one host. Connecting hubs, concentrators, switches, bridges, etcetera…
to this interface when portfast is enabled, can result in temporary
bridging loops. Use with CAUTION
%Portfast has become configured on FastEthernet0/five but will only
have outcome if the interface is in a very non-trunking mode.
SW1(config-if)#
Not merely will the swap alert you about the right use of PortFast, but you will need to place the port into obtain method just before PortFast will acquire result.
Now, you’d feel http://www.bbc.co.uk/search?q=토토사이트 that could well be enough of the warning, appropriate? But there's an opportunity – just an opportunity – that someone will probably take care of to attach a change to your port jogging Portfast. Which could bring on two key difficulties, the 1st being the development of the switching loop. Remember, The explanation We've listening and Mastering modes is to help prevent switching loops. The subsequent problem is that there might be a fresh root bridge elected – and it could be a switch that isn’t even in your community!
BPDU Guard protects against this disastrous probability. If any BPDU is available in on the port that’s functioning BPDU Guard, the port will probably be shut https://totobucks.com/ down and placed into error disabled condition, revealed about the switch as err-disabled. A port put in err-disabled state needs to be reopened manually.
BPDU Guard is off on all ports by default, and is also enabled as revealed here:
SW1(config-if)#spanning-tree bpduguard enable
It’s a good idea to allow BPDU Guard on any port you’re functioning PortFast on. There’s free of charge in overhead, and it does protect against the potential of a change sending BPDUs right into a port configured with PortFast – not forgetting the opportunity of a change not underneath your Regulate getting a root switch for your network!