Cisco CCNP / BCMSN Test Tutorial: Configuring PortFast And BPDU Guard
With your CCNA scientific tests, you acquired about PortFast and The difficulty it might cause if configured on the incorrect port! Suitable only for switch ports linked directly to a single host, PortFast allows a port working STP to go straight from blocking to forwarding 먹튀검증사이트 mode.
A Cisco router will provide you with a warning once 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 many others…
to this interface when portfast is enabled, may cause momentary
bridging loops. Use with Warning
%Portfast has long been configured on FastEthernet0/5 but will only
have impact when the interface is within a non-trunking method.
SW1(config-if)#
Don't just will the switch alert you about the right use of PortFast, but you should set the port into access method in advance of PortFast will just take outcome.
Now, you’d feel that will be more than enough of a warning, appropriate? But there's an opportunity – just a chance – that someone will probably regulate to attach a switch into a port running Portfast. That could result in two major complications, the initial currently being the development of a switching loop. Keep in mind, The key reason why We now have listening and Understanding modes is that will help stop switching loops. Another difficulty is usually that there might be a different root bridge elected – http://www.thefreedictionary.com/토토사이트 and it may be a switch that isn’t even in the network!
BPDU Guard guards towards this disastrous likelihood. If any BPDU is available in on the port that’s running BPDU Guard, the port will probably be shut down and put into error disabled condition, demonstrated over the swap as err-disabled. A port positioned in err-disabled point out must be reopened manually.
BPDU Guard is off on all ports by default, and it is enabled as revealed here:
SW1(config-if)#spanning-tree bpduguard empower
It’s a good idea to enable BPDU Guard on any port you’re working PortFast on. There’s free of charge in overhead, and it does prevent the potential of a change sending BPDUs right into a port configured with PortFast – let alone the potential of a swap not underneath your Manage getting a root switch to the community!