Cisco CCNP / BCMSN Exam Tutorial: Configuring PortFast And BPDU Guard
With your CCNA reports, you acquired about PortFast and the trouble it can cause if configured on the incorrect port! Suited just for change ports connected on to an individual host, PortFast makes it possible for a port jogging STP to go straight from blocking to forwarding mode.
A Cisco router provides you with a warning after you configure PortFast:
SW1(config)#int rapid 0/5
SW1(config-if)#spanning-tree portfast
%Warning: portfast need to only be enabled on ports linked to a
single host. Connecting hubs, concentrators, switches, bridges, and many others…
to this interface when portfast is enabled, might cause momentary
bridging loops. Use with CAUTION
%Portfast has long been configured on FastEthernet0/5 but will only
have outcome if the interface is in the non-trunking mode.
SW1(config-if)#
Not just will 먹튀검증 the swap alert you about the right use of PortFast, but you must set the port into access method just before PortFast will get influence.
Now, you’d believe can be sufficient of a warning, suitable? But there is an opportunity – just a chance – that someone will probably regulate to connect a switch to your port operating Portfast. That may bring on two key troubles, the very first remaining the formation of a switching loop. Try to remember, The main reason We now have listening and Finding out modes is that can help prevent switching loops. The following issue is there may be a new root bridge https://en.wikipedia.org/wiki/?search=토토사이트 elected – and it may be a switch that isn’t even inside your community!
BPDU Guard shields from this disastrous possibility. If any BPDU comes in with a port that’s managing BPDU Guard, the port are going to be shut down and placed into mistake disabled condition, demonstrated within the change as err-disabled. A port put in err-disabled point out must be reopened manually.
BPDU Guard is off on all ports by default, which is enabled as demonstrated right here:
SW1(config-if)#spanning-tree bpduguard allow
It’s a smart idea to allow BPDU Guard on any port you’re managing PortFast on. There’s free of charge in overhead, and it does stop the possibility of a change sending BPDUs right into a port configured with PortFast – in addition to the possibility of a swap not under your control getting a root switch towards your network!