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SGE2000 - SG300 - MGBLH1 - Connectivity/DHCP/VLAN

Hi Experts,

Need your help, advise and support to fix the below issue in bringing our network

Just extended our intranet buildings with Fiber Optic Connectivity with the Following Components

Data Center Building

1. SG2000 - CISCO

2. 24 port LIU - MOLEX

3. GBIC SFP Transceiver - single mode SG300 MGBLH1 - CISCO


New Building with OFC Terminated

1. SG300 Switch SG300-28P (SRW2024P-K9) - CISCO

2. 24 port LIU - MOLEX

3. GBIC SFP Transceiver - single mode SG300 MGBLH1 - CISCO

Post the OFC Termination and Splicing, we are able to get the Link and connectivity through the SFP Ports.

But unable to get the Ethernet Link up and running.

SG2000 is configured to be L3 Mode Switch with couple of VLAN configurations and working perfectly well.

Have configured one of the custom VLAN in the new building and made the DHCP Relay to be passed through,  but it is not passing the DHCP traffic.

But peculiarly, when we connect both the ends with SG300, it works like a charm.

Hence, i went back to basics and checked the SFP compatibility, and alas, the MBGLH1 is compatible with SG2000

Please advise, what additional should be made to extend the network with the above setup.



Hi victvishwa, the SG2000 is

Hi victvishwa, the SG2000 is a very old switch and sometimes does not work expectantly. I may recommend to try a different port on the SG2000, but not just any port. First consider if the switch is in stack mode or not, if it is in stack mode, it uses shared ports that are 'shut down'. Secondly, if the switch is in a standalone mode, if you are using a "top port", try to use the port below it as you may observe the SFP will be turned upside down which could create a cross over. I have seen in the past the SG2000 switches do not automatically cross over the connections which may be the issue.

-Tom Please mark answered for helpful posts

Just as Tom Watts said,To add

Let troubleshoot

1. Are lights lighting up?
    -Try swapping the fiber cables, it may just be in reverse


Check if your modules are compatible by:
#show inventory    -your SFP should be detected

In your SG, you probably need to find it through GUI


IF YOUR SFP SUPPORTS IT, check the signal levels, it may not be
receiving enough signal strength, NOTE: If ever there is no display it is okay,
your SFP may not support static polling
#show interfaces transceiver detail


Do this on both devices,
On the configuration side

Check if you have L2 vlans by #show vlans
vlan.dat may have become corrupted


If ever your SFP is detected,  but still no LED lights, try swapping the fiber optic cable again

Rate or Mark as correct helpful post :)



New Member

Hi.,I am sorry for delayed


I am sorry for delayed reply.

This issue has been addressed and fixed. To update what the issue was.

1. When we connected the SFP Ports to the corresponding locations, link was up but it did get pass traffic through, as I was tailing my DHCP server logs.

2. My ex-colleague helped me to understand, though the SFP ports are separate on this Switch(SG300), the moment we connect a SFP port, one of the ethernet port which lits up has to be configured to our requirements.

3. I had allowed the corresponding Gig port g/11 to allow the specific vlan and enabled the dhcp relay option. It started receiving the traffic on the DHCP Server.


One more Issue was: Only Ports g/11 and g/23 were working out of the Four SFP ports.

While troubleshooting, sh interface commands showed the g/12 and g/24 as blank, and after 3 hours of continuous amateur troubleshooting,

When logged into the GUI mode of the switch and clicked on the port g/12 in the status page, it threw an error stating, that "This is a stacking port and cannot be configured".

Then I disabled the Stacking mode and had to reload the switch to make it work.

It was really an awesome learning and was very interesting to do such stuff.

I am sorry if something were very basic things which I should have done and missed it. Forgive me as I am a system administrator who has deep interests in working with networking.

Please help as I may be posting many other questions like this as I am volunteering my time and support to a non profit organization.

Way to go !!!

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