GigabitEthernet Int. Input & CRC Errors

[markbd111]

I'm getting a lot of errors on this gigabit ethernet interface. It's a multimode fiber GBIC connected to another 3550 multimode fiber GBIC. I thought it might be duplex mismatch or something. Not sure though, I couldn't find a command to change it. Any advice?

output:

4506#sh interfaces gigabitEthernet 2/3

GigabitEthernet2/3 is up, line protocol is up (connected)

Hardware is Gigabit Ethernet Port, address is 0008.e366.xxxx (bia 0008.e366.xxxx)

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

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

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 1000Mb/s, link type is auto, media type is SX

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

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

Last input 00:00:18, output never, output hang never

Last clearing of "show interface" counters 12w3d

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops:0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 478000 bits/sec, 460 packets/sec

5 minute output rate 1856000 bits/sec, 970 packets/sec

710250142 packets input, 112085351005 bytes, 0 no buffer

Received 29160198 broadcasts (22048037 multicast)

6 runts, 0 giants, 0 throttles

12628204 input errors, 5134 CRC, 0 frame, 0 overrun, 0 ignored

0 input packets with dribble condition detected

5150565272 packets output, 1162278860395 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

[Kevin Dorrell]

I would try cleaning the SC connectors as mentioned in the documentation, and then try changing the GBICs. I assume the fiber length is within the limits for the technology.

It it 1000BaseSX? I have seen 1000Base SX links start to fail. Apparently they are cheaper because they are made with cheaper laser diodes as used in CD players, so the wavelength tolerance is a bit loose. Sometimes changing the GBIC can solve these problems.

Normally I start to get worried if the error rate on a 1000BaseSX link is more than a couple of part per billion.

Regarding full- half- duplex, Gbit ethernet is specified only as full duplex.

Otherwise you'll have to get hold of some f/o test equipment and see if the signal is within the power-loss budget.

Kevin Dorrell,

Luxembourg.

[michael.armstrong]

Cleaning the connectors is excellent advice. We had a situation where we just felt "something was wrong" with a Gb link between a 3550 and a 3524, but no errors were logged -- none. We put a f/o Gb cable tester on the link and it wouldn't even sync up the two ends. When examined under the microscope, the ends of the connectors looked like Hurricane Charley's debris field. After cleaning, the tester said things were fine, and the "problem" went away. I'd still like to know why the 3550 reported no errors, but I'm pragmatic enough to accept the results and keep things clean.

[scottosan]

I would still manually set the speed on both switches to 1000

[markbd111]

The normal speed and duplex commands do not work on the fiber GBIC's does it? The speed and duplex settings on both interfaces show gigabit and full-duplex.

[scottosan]

Ibelieve you can set the speed, but not the duplex. I may be wrong.

[Kevin Dorrell]

Gibabit fiber is Gigabit, and you cannot change it. (Unlike Gigabit copper 1000BaseTX?, which will fall back to the lower speeds by negotiation.)

Kevin Dorrell

Luxembourg

[Kevin Dorrell]

Just as an aside to this, if I was running CatOS I would use the very useful command "show port capabilities b/p". This shows you which speeds the port supports, as well as channelling capabilities, trunking, etc. Does anyone know an equivalent command in IOS?

Going back to fibre, the reason you don't have multi-speed fibre ports is that the light wavelength used is different for each standard. 10BaseFL (remember that?) and 1000BaseSX use a visible 1350 nm red lasers (although I wouldn't recommend looking at it too long!), while 100BaseFX and 1000BaseLX/LH use invisible 850 nm light. I don't know any components that have more than one laser diode built in.

Kevin Dorrell

Luxembourg