Sanity Check

[GuyM]

Hi all,

I've just been asked to look at the network in a business I work for.  Part of the configuration has a SG300-28MP manages switch.

What has tripped my mind is that the uplink port G27 is linked to port 17 (yes on the same switch). This seems so insane to me that I'm beginning to doubt myself. Can anyone think of any reason that someone would have done this. I think it just forms a loop that the s/w will kill.

Thanks

Guy

[Karsten Iwen · Accepted solution]

In general, it doesn't make sense at all. I would expect that one port is in the STP blocking state. The port configuration of both ports would be interesting. 

Besides that, this switch is End-of-Support, and you should consider a replacement.

[liviu.gheorghe]

Hello @GuyM ,

it's hard to say why a port on the switch is connected with another port on the same switch. Maybe it's just a mistake done by someone.

Indeed this is a loop, but the switch has a protocol running by default, Spanning Tree Protocol (STP), which deals with this kind of situations. STP breaks loops in a layer 2 network by disabling one of the ports.

Hope this helps.