Fiber

[mkraemer76]

I'm trying to get two 3com switches to uplink via an SFP and mini-gbic with multimode fiber. The switches in question are a 4200 located in my POP and a 4228 located in my downstairs IDF. The downstairs switch i have lights, the logs indicate that its transmitting data but not receiving. the upstairs switch has no lights and no activity. Should i just be able to connect and get lights or is there addtional configuration required? All switches (4 in this stack) are on the same VLAN and subnet. Have verified gbic and sfp are good items. At a loss, any assistance would be great.

 

[spidey07]

you'll have to make sure the transmit goes to receive and vice versa.

swap the individual fibers around to see if you can get link on both ends. Although it's strange that you have link on one end, but not the other unless a single fiber is bad. Also make sure the other fiber port is actually enabled.

one last thing - look at the flow control settings on each port. They need to match. In fact, that's what it sound like....because if you have link on one end your fiber tx/rx should be good. But if the flow control settings don't match you'll have what you describe - link on one end but not the other.

 

[mkraemer76]

i've made sure that everything lines up on TX and RX, flow control is enabled on both sides, my only thought is that the termination box is not punched properly and i don't have the tools to test right now. very strange, thanks for the input

 

[spidey07]

Use a bright flash light to test or just look at the colors of the fiber to make sure you are using the correct ones. It would help if you had a fiber certifier/tester.

DO NOT LOOK INTO THE FIBER IF IT IS ATTACHED TO ACTIVE GEAR.

 

[mkraemer76]

good tip, checked and found that we indeed have 1 light coming through our termination box. still no link light in the main pop.

 

[mkraemer76]

Just spoke with the person i replaced in this company, turns out that the vendor who installed the fiber did a shotty job, had to get them to come out 3 different times to get the previous uplinks to work. just in case you were wondering

 

[spidey07]

sounds like it needs to be tested then. Make them certify it for whatever flavor of gigE you're using.

 

[mkraemer76]

sure will, thanks spidey

 

[spidey07]

one last tip,

cat6/fiber certifiers are worth their weight in gold and are necessary tools for a network. They generally can pay for themselves very quickly.

 

[skyking]

Originally posted by: spidey07
one last tip,

cat6/fiber certifiers are worth their weight in gold and are necessary tools for a network. They generally can pay for themselves very quickly.

I'm buying the parts for it for our cert tester. I could not agree more.