A switch is connected to itself

[vipinrajrc]

Hi Experts,

Recently i have found that one of our clients switch is connected to itself. I understad this using "sh cdp neighbor" command. Is there any special use for this type of connection??? or someone unknowingly connected it?? Does it make any problem llike broadcast stoem..???

Regards

Vipin

[garapoglou]

Hi,

What's exactly the output of sh cdp neighbor command?

Best regards,

Giorgos

[vipinrajrc]

Hi,

Please see the following

SW#sh cdp neighb

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID

SW         Fas 0/9           125           S I      WS-C3560- Fas 0/13

SW         Fas 0/13          125           S I      WS-C3560- Fas 0/9

"SW" is the switch name. Previously infrastructure was managed by some other company. So i am not sure this is for a purpose or not... Please suggest a suitable answer...

Regards

Vipin

[garapoglou]

Hi,

You should unplug the cable which connects switchport Fa 0/9 to Fa 0/13 to avoid broadcast storms. Even if STP is enabled, there's no reason for that connection.

For the record, my guess would be someone didn't check the cable was already connected to the switch and plugged it in on the first switchport available.

Best regards,

Giorgos

[vipinrajrc]

Hi,

Thanks for the reply.. we will remove that cable soon.

Regards

Vipin

[garapoglou]

You're welcome!

Thanks for rating.

Giorgos

[fgasimzade]

Yes, it can be cause of broadcast storms, you should unplug, I see no reason why it should connected to itself

[glen.grant]

  Someone has made a built in physical loop .  Spanning tree probably took care of the potential serious problem .  You can verify with the show spanning-tree blocked ports"  command and i'll will bet that one of those ports shows blocked. Definetly get rid of it .

[vipinrajrc]

Hi Glen

Yes, STP is blocking the that port. 

Thanks,

Vipin