Catalyst 2950 slow thruput

I've got a strange problem that's eating my lunch...

Our central site has a C3750 switch and we have some fiberoptic links to some remote sites with C2950 switches and some Canary 10/100 fiber optic media converters to convert between the single mode fiber and the

100BaseTX copper. One of the remote sites is daisy chained to several other remote sites with C2950 switches and Canary media converters in a "wheel hub and spoke" arrangement such that the net path is like this:

|-CanaryFiberCanary-C2950 | C3750-CanaryFiberCanary-C2950-CanaryFiberCanary-C2950 | |-CanaryFiberCanary-C2950

The distance between the remote sites is several miles, hence the need for single-mode fiber, and it was installed in this physical arrangement between sites before I came along, or I would have had it installed all as home runs back to the central office. The "center" C2950 has no hosts at all, it is merely at a location that spreads the network out to the other locations.

I'm getting abysmally slow thruput to the far end points of this rube goldberg fiber optic WAN. Like around 5-6Mbps when trying to copy a 4GB file from a Windows host on the C3750 to a Windows host on the far-end C2950, when it sould be close to the 100Mbps theoretical max thruput.

All the C2950 switches are very plain-jane configuration... out of the box, with an ip address given to vlan1 and manual speed and duplex settings on the ports that are connected to anything.

The fiber segments between sites have been verified to not have any excess dB loss and the Canary units' LEDs show a solid link light on the fiber sides. All fiberoptic patch cables have been tested good too.

All the Canary media converters have been verified to be working properly by substituting a known good unit in place. All devices are hard-configured to 100Mbps and full-duplex, and all switch ports they connect to have been verified to be configured at 100 and full duplex as well. We've *exhaustively* ruled out the usual duplex mismatch problems. All Windows hosts at each end are also verified to be nailed at 100/fullduplex and have no problems talking at full speed to other hosts located at their same respective ends plugged into the C3750 or C2950 switches.

We also have another fiberoptic WAN segment going from that very same C3750 at the central office, also using single-mode fiber over a couple miles away, but using Transition Networks brand 10/100 media converters instead of Canary, and a series of 3 cheap Linksys 10/100 switches at the far end, daisy-chained together to cover a long distance via CAT5, so it looks like this:


This frankenstein monster of a hybrid WAN link gives me about 65-70MBps thruput when copying the same 4GB file, which is absolutely wonderful compared to the mess constructed from the C2950's and Canary converters.

Is there some kind of known problem with Canary fiberoptic media converters and Cisco C2950 switches or something? Can anybody think of any other reasons why I'm getting about half 10BaseT speeds thru this mess? There are no error messages in the logs either. I'm about to pull my hair out over this one.

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One's Too Many
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Ugh, my ascii art drawing didn't turn out like I'd planned.

The top and bottom " |-CanaryFiberCanary-C2950" pieces are supposed to be shown connected to that middle C2950. I guess the blank spaces are getting rendered with variable proportion fonts of something.

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One's Too Many

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