sg300 port problems

[syildirim]

I have a very standard setup. SG300 52 poe, vlan1 and vlan3. Polycom phones on Vlan3. 4 or 5 ports on the switch aren't working as expected. 

I plug the Polycom phone to the bad switch port and it powers but then displays Dhcp failed. Every other port on the switch works except those 4 or 5. No logical explanation. I connect the phone to the other ports and it works. It has a dial tone. Any suggestions? Can couple ports go bad on the switch? Thanks.

[marce1000]

 - Couple of ports can easily go bad. Try some other equipment on the suspicious ports such as laptop (e.g.) ; check the results.

 M.

[syildirim · Accepted solution]

I was able to find the problem. The port wasn't tagged with vlan3. Cisco switches are sensitive. No idea why the port wouldn't tag itself as Vlan3.