Cisco CCNP / BCMSN Test Tutorial: Configuring PortFast And BPDU Guard
With your CCNA experiments, you acquired about PortFast and the trouble it can result in if configured on the wrong port! Suitable just for swap ports related on to an individual host, PortFast enables a port operating STP to go directly from blocking to forwarding mode.
A Cisco router offers you a warning when you configure PortFast:
SW1(config)#int fast 0/5
SW1(config-if)#spanning-tree portfast
%Warning: portfast ought to only be enabled on ports connected to a
single host. Connecting hubs, concentrators, switches, bridges, etcetera…
to this interface when portfast is enabled, may cause non permanent
bridging loops. Use with CAUTION
%Portfast has been configured on FastEthernet0/five but will only
have influence when the interface is within a non-trunking mode.
SW1(config-if)#
Not only will the swap warn you about the correct use of PortFast, but you must set the port into access mode ahead of PortFast will take influence.
Now, you’d imagine that would be more than enough of the warning, suitable? But there is an opportunity – just a chance – that someone will probably deal with to attach a swap to a port jogging Portfast. That might produce two significant issues, the primary becoming the formation of a switching loop. Bear in mind, The main reason We have now listening and Studying modes is that will help stop switching loops. The next trouble is always that there might be http://www.thefreedictionary.com/토토사이트 a fresh root bridge elected – and it may be a swap that isn’t even in your network!
BPDU Guard guards in opposition to this disastrous likelihood. If any BPDU comes in on a port that’s working BPDU Guard, the port will probably be shut down and positioned into error disabled condition, proven about the switch as err-disabled. A port placed in err-disabled state has to be reopened manually.
BPDU Guard is off on all ports by default, and is also enabled as proven below:
SW1(config-if)#spanning-tree bpduguard permit
It’s a smart idea to help BPDU Guard on any port you’re functioning PortFast on. There’s free of charge in overhead, and it does prevent the possibility of a change sending BPDUs right into a port configured with PortFast – as well as the potential for a 먹튀검증 change not less than your Manage starting to be a root change on your network!