Problems with Gigabit Media Converter

[azev]

Anybody used Gigabit media converter to connect between switches with success ??
I'm trying to connect a switch with gigabit fiber uplink to a copper gigabit switch and having some serious issue.

sending data from the switch with fiber connection to the copper switch are extremely slow, but the other way around traffic is moving at normal switch.

I figure this could be flowcontrol issue, but I've tested every possible setting with flowcontrol and it still very slow.

any ideas of what could be the problem ???

Thx

 

[spidey07]

What exactly are the media converters in use, part number would be great, along with the switch model numbers and software versions.

Could be cabling, especially since it's one way.

A common mistake is using 50 and 62.5 micron fiber on the same link/channel. This results in just enough loss to cause problems.

 

[azev]

The hardware is a dell 5324 switch and cisco 5505 switch with sup III and gigabit uplink module.
The media converter is planet brand, not sure the model no.

The dell switch actually have sfp fiber uplink, but my client does not want to run fiber from the dell switch location to the cisco switch location. They wanted to use the exisiting copper cat5e wiring.

The dell switch is connected to the serverfarm (8 servers total) and the cisco switch connected to all the cubes and offices.
I am pretty sure that the fiber we're using is a 3ft 62.5micron with sx connector.

And yes the problem is one way, and in this matter the worse possible problem. The client cannot download faster than 5mbps/s from the server, but the server can download file from a client machine at a full 10/100 speed.

Enabling flowcontrol worsen the problem.

any ideas ??

anyway, uplink directly to one of the 10/100 ports on the switch solved the problem, but not what they want. They wanted to have a gig of uplink to the server switch.

 

[spidey07]

I'm confused.


You are taking 1000 Base-T ports (copper) on the dell and cisco switch and then using two gigabit media converters to connect the switches?

dell copper port----media converter---fiber---media converter---cisco copper port?

But this is starting to sound like a cabling problem or a duplex mismatch on one end. So check the errors on the switch ports in question and make sure the speed/duplex is set properly (hard code both ends or auto on both ends)

Another thing to check would be speed/duplex settings and errors on the server just to get that out of the way.

 

[azev]

its actualy alot simpler that that,

dell copper port ------- copper cable------ all the way to the cisco switch closet-------- media converter -------- fiber -------- cisco fiber 1Gbps port.

I am very sure that no duplex mismatch between the 2 devices..... I've disabled negotiation on both device and hard set the speed to 1000.

port counters on both switch does not show any errors either, weird eh ??

 

[spidey07]

Well technically the media converter is another layer1 device, so the errors could be on it.

Normally if it is a flow control problem you won't get link.

Try auto negotiation on both switches for speed duplex. You may be forcing the switch to 1000/full, but the media converter is running 1000/half becuase it is doing autonegotiation.

Can't rule out cabling until the cable is certified cate 5e with a tester.

I'm still really thinking it is duplex though as that's the kind of symptoms you get.

-edit- there should be something on the media converter that tells you speed/duplex like some LEDs. There may even be dip switches to set it's operation. The model number of the converter would be very helpful.

 

[azev]

I called them and the media converter model is GT-702 from planet
here's the link for it http://www.planet.com.tw/product/product_dm.php?product_id=28&menu_id=13
I'll be there after work to troubleshoot the problem again, and I'll pay attention to duplex more carefully.

 

[spidey07]

I wan't my cut of the fee.

After thinking about it some more, I'm pretty sure it is a duplex problem on the 1000 Base-T port of the media converter. Unless this port was forced to 1000/full it is running in 1000/half mode.

that's what will happen if one side of a link is forced to full duplex, the side that is at auto will fall back to half duplex because it didn't receive any autoneg information. So setting the switch port this is attached to to auto should resolve it.

 

[cmetz]

spidey07, ain't no such thing as 1000/Half. At least not in the spec. 1000 is always full duplex.

azev, media converters are trouble. If at all possible, get the appropriate GBICs for your gear and put the fiber in directly. If not possible, then try getting a MILAN one as a replacement. They've been recommended by several ISPs whose testing guys I trust.

 

[spidey07]

cmetz,

you're talking about fiber gig ethernet, which is full only.

1000 Base-T does autonegotion similar to 10/100 and suffers the same issues.

 

[cmetz]

spidey07, my understanding of the standard for 1000BaseT is that there is NO half duplex mode. This is of course unlike 10BaseT or 100BaseTX. I will have to pull up the spec to confirm.

 

[gordita]

my experience tells me....
#1) check cat5e to make sure all 4 pairs are terminated at each end.
#2) if the converter has dip switches, refer to the manual and make sure it's set for full duplex AND if there's still a problem, play around with the config of the dip switches.
ofcourse, make sure the ports on the cisco and dell are operating at full gig

 

[azev]

Ok, I figure out what is problem.
Apparently one of the builtin GBIC on the uplink card is bad.
I went and look at the gbic to see the tx laser, and the first port is very dimmed compared to the other one. ( I know this is bad, but I did it anyway )

after using the other ports as the uplink, it kinda fixes the problem.
There's still some speed issues even when using the other gbic, my assumption is both GBIC is probably about to die soon.

maybe its time for them to replace that old 5505

thanks for all the help guys.