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New Member

Connecting GBIC to GBIC with fiber cable

Hi,

I am connecting a 3550-12G and a 2950-48 GBIC to GBIC with SC-SC fiber optic cable and the lights fail to indicate any connection. I have tried several slots and cables.

What am I doing wrong?

TIA

George

1 ACCEPTED SOLUTION

Accepted Solutions
Gold

Re: Connecting GBIC to GBIC with fiber cable

First, check to see whether the Gigabit Ethernet ports in question are in a "shutdown" or "administratively down" state.

What kind of fiber optic GBICs (SX, LX/LH, ZX)?

What kind of fiber optic patch cables? Multimode (generally orange, can be other) or single mode (generally yellow, can be other as well)?

SX uses multimode fiber only. LX/LH can use either at distances under 250m; from 250m to 550m, special mode conditioning launch/patch cables are needed to run LX/LH over multimode fiber; running LX/LH over just single mode fiber is good to 5-10km. ZX uses single mode only; and if you do patch cable test connections in a lab setting, you also need at least an 8dB inline attenuator on each RX port to protect the receive optics. (10dB attenuator is more common.)

Have you tried swapping the connectors in the TX and RX ports at one end?

If you have two SX GBICs, one in each switch, and the distance between the two switches is short, then a multimode patch cable between the two switches is all that's needed. If you click each SC connector in securely and have no link light/activity, you probably have transmit from one GBIC patched into transmit of the other. So on one GBIC, swap the connectors: the one that was in TX port, put it in the RX instead; and the one that was in RX, put it in TX port instead. This will give you a proper crossover.

Note: some duplex patch cords (Corning or Siecor, for example) have the two SC connectors held together by a clip; you can slide the individual connectors out to the side to free them up for doing the cross-over. I have seen others (Amp?) where the two SC connectors appear to be snapped together, and are tough to separate. But it can be done, with careful twisting or a sharp utility knife.

If swapping the connectors at one end doesn't work, you may have a bad patch cable. To do a quick-and-dirty test, you'll need one GBIC to plug into. Plug in one SC end to the TX port, then trace that fiber strand down the patch cable to the other end and plug that SC connector end in, creating a loop between the TX and RX port. If you get a link, then that strand is OK, DISCONNECT IT AT ONCE so you don't create a broadcast storm. If no link, then that strand or a connector may be bad. If several patch cables test bad, find a known good one and run the same test to see if the GBIC is bad. Remember, you have to use the correct fiber type for the GBIC you're plugging into.

Hope this helps.

6 REPLIES
New Member

Re: Connecting GBIC to GBIC with fiber cable

Can you please do a post show run on the gigabit interface for each switch to see if you have configured the switchports correctly?

DTA

New Member

Re: Connecting GBIC to GBIC with fiber cable

Hi Here are the shows, I dont have the contracts yet on these switchs so I can download the CMS browser plugin so I was trying to setup from the console.

Cheers,

PDP-3500>sh int gi0/1

GigabitEthernet0/1 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 000d.ed3f.4c80 (bia 000d.ed3f.4c80)

Internet address is 192.168.1.8/24

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Auto-duplex, Auto-speed

input flow-control is off, output flow-control is off

ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output never, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue :0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute ouxtput rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 0 multicast, 0 pause input

0 input packets with dribble condition detected

0 packets output, 0 bytes, 0 underruns

0 output errors, 0 collisions, 2 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

0 output buffer failures, 0 output buffers swapped out

PDP-2950-A>sh int gi0/1

GigabitEthernet0/1 is down, line protocol is down (notconnect)

Hardware is Gigabit Ethernet, address is 000d.bd91.9ef1 (bia 000d.bd91.9ef1)

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Auto-duplex, Auto-speed

input flow-control is off, output flow-control is off

ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output 02:06:46, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue :0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute ouxtput rate 0 bits/sec, 0 packets/sec

1 packets input, 64 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 0 multicast, 0 pause input

0 input packets with dribble condition detected

1 packets output, 64 bytes, 0 underruns

0 output errors, 0 collisions, 3 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

0 output buffer failures, 0 output buffers swapped out

New Member

Re: Connecting GBIC to GBIC with fiber cable

In the show int output. I don't see the

"Auto-duplex , 1000Mb/s, media type is SX" showing the GBIC modules inserted.

Console into the switch and show output of command.

"sh int status" and see if you see an output like this? "Gi0/1 otconnect trunk Auto 1000 1000BASESX

Gi0/2 notconnect trunk Auto 1000 CX_GIGASTACK" depending on what Gigabit module you use. If not and the GBIC's are inserted. Was the GBIC's inserted when the switch was powered on?

DTA

Gold

Re: Connecting GBIC to GBIC with fiber cable

First, check to see whether the Gigabit Ethernet ports in question are in a "shutdown" or "administratively down" state.

What kind of fiber optic GBICs (SX, LX/LH, ZX)?

What kind of fiber optic patch cables? Multimode (generally orange, can be other) or single mode (generally yellow, can be other as well)?

SX uses multimode fiber only. LX/LH can use either at distances under 250m; from 250m to 550m, special mode conditioning launch/patch cables are needed to run LX/LH over multimode fiber; running LX/LH over just single mode fiber is good to 5-10km. ZX uses single mode only; and if you do patch cable test connections in a lab setting, you also need at least an 8dB inline attenuator on each RX port to protect the receive optics. (10dB attenuator is more common.)

Have you tried swapping the connectors in the TX and RX ports at one end?

If you have two SX GBICs, one in each switch, and the distance between the two switches is short, then a multimode patch cable between the two switches is all that's needed. If you click each SC connector in securely and have no link light/activity, you probably have transmit from one GBIC patched into transmit of the other. So on one GBIC, swap the connectors: the one that was in TX port, put it in the RX instead; and the one that was in RX, put it in TX port instead. This will give you a proper crossover.

Note: some duplex patch cords (Corning or Siecor, for example) have the two SC connectors held together by a clip; you can slide the individual connectors out to the side to free them up for doing the cross-over. I have seen others (Amp?) where the two SC connectors appear to be snapped together, and are tough to separate. But it can be done, with careful twisting or a sharp utility knife.

If swapping the connectors at one end doesn't work, you may have a bad patch cable. To do a quick-and-dirty test, you'll need one GBIC to plug into. Plug in one SC end to the TX port, then trace that fiber strand down the patch cable to the other end and plug that SC connector end in, creating a loop between the TX and RX port. If you get a link, then that strand is OK, DISCONNECT IT AT ONCE so you don't create a broadcast storm. If no link, then that strand or a connector may be bad. If several patch cables test bad, find a known good one and run the same test to see if the GBIC is bad. Remember, you have to use the correct fiber type for the GBIC you're plugging into.

Hope this helps.

New Member

Re: Connecting GBIC to GBIC with fiber cable

Hi guys,

Swapping the TX and RX worked. Thanks! Forgive the green guy here.

Cheers,

G

Gold

Re: Connecting GBIC to GBIC with fiber cable

Glad to hear it's up!

Keep an eye on that link, though. Run some tests across it periodically to benchmark the performance. I've run some Gigabit Ethernet LX/LH connections past the specified distances on SMF with no problems. But whenever you exceed the specs, you're on your own: you're the one responsible for whether or not it works.

I've personally seen LX out to 16km work, and ran several large file transfers at various times to verify reliability. But I've also seen a customer try to run LX out to 20-22km. That connection sort of seemed to fade in and out, and was too unreliable to use. When we replaced the LX with ZX GBICs and 10dB attenuators, it worked fine.

Keep us posted on your experiences with SX over multimode out to 1km. I think you may be in uncharted territory. :)

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