Showing results for 
Search instead for 
Did you mean: 


Introducing the next generation of Cisco Small and Medium Business Switches. Cisco is refreshing its SMB Switch portfolio. Click here  to learn more.


SG300 Optical Module did not Work


I have two SG300-20 Switches and buy two MGBLX1 Modules for the Switches.

I plugedin the Modules but the Modules didn`t work and in the WebConsole i can´t see the Modules.

10-06-2011 21-02-53.png

Is there any configuration to enable the SFP Modules? or is it a problem from my Switches

Has anyone an idee?

Regards Dominik

David Hornstein
Rising star

Hi Dominik,

I'm going to ask some simplistic questions regarding;

1.  Type of fiber you are using, as you may have some cabling issue

2.  Have you checked the error log to see if the switch sees the insertion of a SFP

3.  Diagnostic > Optical Module Status good way to check what's happening with SFP

4 . maybe a quick loopback test for a quick visual indication that the SFP may be working.


On the side of the fiber it should say 9um  (micrometers) which is single mode fiber,  maybe even a yellow coloured fiber pair.  If the cable is not 9um single mode cable most likely the installation will NOT work.  You realize that the fibers have to be crossed over so that a transmit port on one SFP  has to be sent to the remote receive port on the remote SFP.

Error log

But, you should check if the error log  notes the insertion of a SFP,

When i look at my System summary the fiber port is treated with precedence over the copper port when both are used.  So if there is no link you will not see a green LED icon on the System Summary page to indicate a link.

If you check my partial error log copy and paste below,  you will see  i plugged my SFP into slot GE10 of my SGE300-10P (SRW2008P-K9-NA)

2147483597          2011-May-23 22:48:14          Informational           %Fiber-I-SFP-PRESENT-CHNG: gi10 SFP status is present., aggregated (2)     

2147483600          2011-May-23 22:48:06          Informational           %Fiber-I-SFP-PRESENT-CHNG: gi10 SFP status is present.     

2147483601          2011-May-23 16:45:40          Informational           %INIT-I-Startup: Cold Startup  

If you do not see SFP entries in your error log, maybe the SFP is defective, but lets remove the SFP and kindly ask someone else in your office  to insert the SFP.

Did you see any error log entries referreing to SFPs?

Optical Module Status

Ok,  lets check the diagnostic state of the SFP ports, as per my screen capture below.

It shows GE10  RX and TX power levels , refer Admin guige page 59 for more details;

Do you see any output or input power levels, or a empty row representing the port the SFP is inserted into ?

(Maybe paste a screen capture of this page.)

Radical Diagnostic

Your error log shows a insertion of a SFP, Optical Status will potentially show you power levels and if the SFP  has loss of signal.

If the SFP is inserted correctly, and hasn't been zapped by Electrostatic Discharge (ESD)  from incorrect handling there is one last thing you can try;

With a single fiber (not dual fiber patch)  patch the Transmit port to the Receive port on the SFP module  and you should see a link light  on the front of the switch turn green..This indiactes that light from the light Transit port  is reaching the light  Recieve port.   But probably is causing a loop if you keep the cable connected.

Please do not keep the fiber inserted for more than a second or two. 

Did you see the switch port link light turn green ?

regards Dave

Hi Dave

I looked into hte logs - i see when i plug in the sfp the init but i can´t see it in the optical modules.

i have two sfp and two switches the problem is same on both switches



Hi Dominik,

I understand that English is not your first language.

I suggest you call the Small Business Support Center (SBSC) tomorrow morning and show them this post.

If you ring in your morning, most likely you will reach the European SBSC.  They are more likely to be able to speak your native language,

My apologies, but there seems to be too many unanswered questions in your post, and I am not smart enough to speak more than one language.

regards Dave

Are there any decision, I have same problem and nothing happens !

My topic is here

Recognize Your Peers
How would you describe your level of technical expertise?