Showing results for 
Search instead for 
Did you mean: 

Fiber Optic in HP switches

Occasional Contributor

Fiber Optic in HP switches

June 24, 2002 15:53 PM GMT


I'm replacing 3com superstack 500 hubs with HP switches (a 4108 in the server room and 2524s in each division). The 2524 switches have fiber modules in them to connect to the 4108gl in the server room. Heres the situation:

The fiber goes into each area and ends at a black box which I refer to as the fiber patch panel. From the patch panel a patch cord comes out and goes into the fiber module in each hub/switch. The fiber patch panel has an SC connection (female) and the hub has an SC connection (as do the new switches) (female). The patch cords have male connections at each end to connect the patch panel to the hub or the switch.

I came in over the weekend to test out the new 4108gl switch with the network and the fiber backbone. I was able to connect a PC to the server, when the server was directly connected into one of the ports on the switch where the PC was, but I was unable to get the fiber modules to function. The leds for the modules didn't light up when I plugged in the fiber patch cord. I checked the status of the modules in the HP management software but I still didn't have anything to show a problem or any connectivity.

I did a hot swap of one of the modules and it showed up in the software with a CRC alignment error and told me to check the duplex situation on the connection modules (half duplex vs. full duplex on the connecting hubs).

Since I was trying to get the new switch to access the fiber off of the old hubs in a different division, I didn't want to replace the other hub(s) just yet. That's planned for this Friday. I want to replace all the hubs with the new switches but I'm afraid that the fiber modules will have this same issue.

Is the issue that I have the 4108 trying to talk to a 3com hub and I need to change the hubs to the 2524s so it will work? Or is there a setting within the 4108 config that needs to change?

Any feedback would be a great help.

Thank you,
Erwin Zoer
Trusted Contributor

Re: Fiber Optic in HP switches

Hello Stephanie,

I think it would be wise if you tried the following:

- Configure the fiber module with a fixed speed matching the 3Com hub's speed setting. Make sure the duplex mode is set to half duplex. Also make sure the cable is correctly connected to the fiber module. That is TX -> RX and RX -> TX. If you're not sure and you do not get a link after making the configuration changes, try to swap the connectors if you do not get a link.
- Test connectivity from the 4108 to the 2524 using the same FO cabling and the optimal settings: maximum common speed and full duplex. If this works but communication from the 4108 to the 3Com hub does not, there may be a compatibility problem as you suggest in your message.

Should none of the tests above work, then it is possible the CRC errors are pointing to a cabling problem. In that case I would verify that the cable is within the required specifications for 100/1000Mb Ethernet.

I hope this helps.


Re: Fiber Optic in HP switches

Hello Stephanie,

what type of transceiver do you use in your 4108 and 2524 ? are they J4853A (100BaseFX) or J4131B (1000BaseSX).

I guess the 3com hubs are old 10 MB ones, is that right?