Re: 6509 problem with LX GBIC

jerad · ‎05-15-2003

Need help figuring this one out. Currently we have 2 remote offices connected via MMF. These offices are on the same campus but across a parkinglot so we're not talking about miles of MMF here. There is a 3548 in each of the offices connecting to desktops. There is 1 MMF running from the MDF to each IDF connecting the 3548 with another 3548 using LX GBICs. When I try to move the GBIC and its patch over to our 6509 I lose connectivity to those remote switches. Why would this work off a 3548 but not off the 6509???? Your help is appreciated.

carenas123 · ‎05-21-2003

What kind of issues you are facing with the GBIC on 6509. I find couple of documents explaining the GBIC issues with Cat6K. Check if you have any of those issues

http://www.cisco.com/pcgi-bin/Support/browse/psp_view.pl?p=Hardware:Cat6000&s=Troubleshooting

jerad · ‎05-22-2003

thanks for the reply. I looked over the documentation and can not find this issue. I'm probably looking in the wrong places. It looks as if this is an issue between the GBIC and the blade on the cat. I have tried numerous ports so i'm sure its not a dead port on the cat. here is a better explanation.

Current setup: Cat 6509 connected to SX GBIC, other end of the SX is in GB port 1 on 3548(1) switch. GB Port 2 has an LX GBIC that runs across parking lot to GB port 1 on 3548(2). The 3548(2) is connected to desktops in that building.

Corrected setup attempt: I moved LX GBIC from GB port 2 on 3548(1) over to 6509. Plugged in and got a link light (green) on back of blade. Could not ping after letting it sit for an hour. Pulled LX GBIC from 6509 and returned it to the same place on 3548(1) and ping was quickly restored.

The documentation i've found indicated that I need a conditioning cable when using the LX GBIC for longer runs. I do not believe this is the problem since the current setup does work using 3548(1) as a basic media converter. This is not a usable setup and must be corrected. This is also the same case on another switch in another building across the parkinglot. Same setup with 3548 as a media converter. This one is also working so i'm confident this is not an isolated issue with 1 GBIC or port. Neither would work in the above tested resolution. I also have several SX GBICs on the same 6509 providing connectivity to our IDFs. Please help!

rjackson · ‎05-22-2003

I think if you read the doc closer you'll see that you need the conditioning cable anytime you use lx gbics on MMF. The only reason to use the LXs is for longer runs. As I recall that is anything over 900ft. 8 of our 9 closets use lx gbics with conditioning cables on both ends. We have the same combo of 6509 and 3548s.

SMF and MMF use differents parts of the fiber. I think SMF shoots down the middle and MMF bounces around the edge. I may be wrong there. But the point is that the conditioning cable allows the lx (made for smf) gbic to use the mmf. It may work without it but its not in spec so when it doesnt work you cant complain. If it was determined that the distance required lx's then you need the conditioning cables. Sorry, they aren't cheap.

jerad · ‎05-22-2003

Thats what I was thinking. I know the "proper" configuration is using the cables and I don't have a problem obtaining them. I guess I was just curious about why it didn't work on the 6509 when it does on the 3548. Does anyone know if there is some sort of power difference or something between the 2 that would cause this to happen? I just want to be sure that the cables are going to correct the connectivity issue once and for all before making the purchase.

Thanks all for your help in this.

richgodfrey · ‎05-23-2003

Just to re-iterate what Rjackson said. SMF uses 9/125 fibre, which is completely different to MMF which uses 62.5/125 fibre. The 9 and the 62.5 represent the core size that the light beam uses within the fibre. I would be very surprised if you managed to run LX over MMF without a conditioning cable, the dispersion of the laser beam that results, means that if you do get a connection, your packet loss is going to be very high. If the packet loss goes too high, the switch may even disable the port. This is not to say it might not work, if it is a relatively short distance, then by some miracle you may get a link (haven't tried this myself though).

Use a conditioning cable with an LX GBIC if the distance of your Multimode fibre is over 280 metres (although I have pushed SX over MMF to 330 metres without packet loss). If it is less than 280 metres then an SX GBIC will suffice.

Hope this helps.

jerad · ‎05-23-2003

thats the exact info I was needing. It now looks as if the LX GBIC is generating errors, the 3548 doesn't seem to care about it though and continues trying to retransmit. The 6509 probably sees the same errors but will instead shut the port down. I do get a link light on both but the communication only takes place on the 3548 which was giving me fits trying to figure it out. I am going to take the building down today in an hour and i'll try running SX across and see what I get. If I do not get connectivity i'll be purchasing a set of conditioning cables for this. We have approx. 800' MDF to IDF of fiber between the 2 so I don't see a reason to run LX. Thanks all for the info, I have had no documentation @ this facility so its all just running with feelers on around here. This board has been an invaluable resource to me. Thanks again!

jerad · ‎05-27-2003

Ok, got the whole link set up with the SX GBIC in place with no problems. Port errors are none at this point, however I still run into the same problem. When I connect up to the 6509 I get link lights on both sides but no data. This is happening in 1 building. There is a second remote building about the same distance from the IDF and it was set up on SX and is currently running on the 6509. I have even tried ports known to be good running other IDFs with the same switch on the other side (3548) and get the same results. Could there be a problem with the fiber run to the remote building?? I'm going crazy with this one so your help is appreciated.