Why the host ports are also seen in the spanning-tree output ?

[chandra_rc16]

Why the host ports are also seen in the spanning-tree output ?

Switch1#show spann

VLAN0001

  Spanning tree enabled protocol ieee

  Root ID    Priority    32769

             Address     0000.0CA2.138B

             This bridge is the root

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

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)

             Address     0000.0CA2.138B

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

             Aging Time  20

Interface        Role Sts Cost      Prio.Nbr Type

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

Fa0/1            Desg FWD 19        128.1    P2p

Fa0/2            Desg FWD 19        128.2    P2p

Fa0/15           Desg FWD 19        128.15   P2p

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

!

interface FastEthernet0/15

description PC0 Interface

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/16

I read somewhere that all the ports of a switch will participate in STP by default. Is there any way to remove the STP operation on host ports ?

Regards,
Chandu       

[devils_advocate · Accepted solution]

All ports participate in Spanning Tree by default.

Spanning tree is there to block redundant L2 paths in order to prevent loops. All ports are capable of causing a loop so you would not want to turn spanning tree off, in fact I don't think you can switch it off on a per port basis. You can switch it off on a per vlan basis.

You are already using portfast which allows host ports to transition into a forwarding state without going through the listening and learning states of STP. If you switch off STP on a port, you risk the chance of a L2 loop.

https://supportforums.cisco.com/docs/DOC-5180

[chandra_rc16]

Hi

When my switch is connected to a host.. how can it turn in to a layer2 loop ?

Actually i thought to remove it because... it will be bit harder to see the spanning-tree output if  40 ports out of a 48 port switch are used to connect hosts .

Regards,
Chandu

[devils_advocate]

If the port is configured correctly, in theory, it cannot. However its possible, hence why STP runs on all ports.

[Jon Marshall · Accepted solution]

Chandu

Hosts are there because to the switch it is just another port ie. the swith has no idea what is connected to the port.

It normally can't become a L2 loop but STP still has to run on that port and you don't want to disable it.

Jon

[chandra_rc16]

Thanks for you both for the help.

So final conclusion is  we've to bear that stuff on the STP output...

Regards,
Chandu