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what is the command that shows that port-fast is enabled on certain ports.

How to see whether port-fast is enabled on a port or not ?

Here port fast is disabled globally.

switch0#sh span sum

Switch is in pvst mode

Root bridge for:

Extended system ID           is enabled

Portfast Default             is disabled

O/p of show spanning tree:

switch0#show spanning-tree

VLAN0001

  Spanning tree enabled protocol ieee

  Root ID    Priority    1

             Address     00D0.5865.B7E7

             Cost        19

             Port        1(FastEthernet0/1)

             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    28673  (priority 28672 sys-id-ext 1)

             Address     000A.F3D2.55D2

             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time  20

Interface        Role Sts Cost      Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/1            Root FWD 19        128.1    P2p

Fa0/2            Altn BLK 19        128.2    P2p

Now i enable port-fast on Fa0/2. (Just doing trial and Error to understand things a better)

switch0(config)#interface fastEthernet 0/2

switch0(config-if)#spanning-tree portfast

%Warning: portfast should only be enabled on ports connected to a single

host. Connecting hubs, concentrators, switches, bridges, etc... to this

interface  when portfast is enabled, can cause temporary bridging loops.

Use with CAUTION

%Portfast has been configured on FastEthernet0/2 but will only

have effect when the interface is in a non-trunking mode.

switch0(config-if)#switchport mode access

switch0(config-if)#end

Now, where what is the command that shows that port-fast is enabled on certain ports.

REgards,

Chandu

Regards, Chandu
4 REPLIES

what is the command that shows that port-fast is enabled on cert

Hi,

try this one:

#sh spanning-tree detail | inc FastEthernet|portfast

Hope it will help.

Best regards,
Abzal

Hope it will help. Best regards, Abzal
Community Member

what is the command that shows that port-fast is enabled on cert

Got it. Since the port-fast enabled ports doesn't participate in STP. There is no Fa0/1 port in o/p of sh span tree detail.

switch0#show spanning-tree detail

VLAN0001 is executing the ieee compatible Spanning Tree Protocol

  Bridge Identifier has priority of 0, sysid 1, 000A.F3D2.55D2

  Configured hello time 2, max age 20, forward delay 15

  Current root has priority 1

  Topology change flag not set, detected flag not set

  Number of topology changes 0 last change occurred 00:00:00 ago

            from FastEthernet0/1

  Times:  hold 1, topology change 35, notification 2

          hello 2, max age 20, forward delay 15

  Timers: hello 0, topology change 0, notification 0, aging 300

Port 2 (FastEthernet0/2) of VLAN0001 is designated forwarding

  Port path cost 19, Port priority 112, Port Identifier 112.2

  Designated bridge has priority 1, address 000A.F3D2.55D2

  Designated port id is 112.2, designated path cost 19

  Timers: message age 16, forward delay 0, hold 0

  Number of transitions to forwarding state: 1

  Link type is point-to-point by default

Regards,

Chandu

Regards, Chandu
Community Member

Re: what is the command that shows that port-fast is enabled on cert

The Best command to see simply if portfast is enabled for example on port fastethernet 1/0/1

S1#show spanning-tree detail | s Port 1

S represents section 

1 is the number or tag of your interface 

For my example look the result

switch_off_vau#sh spanning-tree detail | s Port 1

Port 1 (FastEthernet1/0/1) of VLAN0010 is designated forwarding

   Port path cost 4, Port priority 128, Port Identifier 128.5.

   Designated root has priority 32778, address 00cc.fc32.f180

   Designated bridge has priority 32778, address 00cc.fc32.f180

   Designated port id is 128.5, designated path cost 0

   Timers: message age 0, forward delay 0, hold 0

   Number of transitions to forwarding state: 1

   The port is in the portfast mode

   Link type is point-to-point by default

   BPDU: sent 149814, received 0

 On red it show you the portfast is enabled

 

Super Bronze

Re: what is the command that shows that port-fast is enabled on cert

"Since the port-fast enabled ports doesn't participate in STP."

BTW, that's not correct. Port-fast ports just skip the initial stages of a STP coming on-line.
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