Issues with 2950 and Linksys switches

Unanswered Question
Jun 24th, 2008

I have been seeing some odd issues between my 2950 and the Linksys Gigabit switches people are using in their cubicles. Their network connections are dropping off quite suddenly.

Only when users force their connection to 100 meg full duplex does the issue seem to fix itself.

I have disabled spanning tree portfast on all the 2950 ports. Not much I can do with the Linksys SD2008 gigabit switches, however.

I have replaced the gigabit switches with 100 meg Linksys switches and that seem to fix the issue, particularly with VOIP connections.

Am running IOS (tm) C2950 Software (C2950-I6K2L2Q4-M), Version 12.1(12c)EA1a, RELEASE SOFTWARE (fc1) on my 2950.

Am wondering if anyone else has had issues with 2950 and Linksys switches or if there is a known issue and if I should update to a newer release?


I have this problem too.
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mohammed_moustafa Tue, 06/24/2008 - 05:59

Hi Kerry,

did you try to make the speed and duplex of your 2950 switch ports connected to Linksys switch auto speed ?


kerryjcox Tue, 06/24/2008 - 06:46

Yes, I manually set the speed and duplex on the cisco ports to 100 full. No effect. We had VOIP phones dropping constantly as they connected through the gig Linksys switches.

Had a similar issue with my T61 Lenovo laptop. Connected through the gig Linksys switch then to the Cisco 2950, I could only connect at 10megs. Hard coding dropped the network connection entirely. The port is a gig port on my laptop.

But when I placed a C2924 switch before the Linksys and plugged in there, was able to connect at 100 meg full, no problem.

Mostly an annoyance, but was hoping there was a fix to the Cisco switches. Linksys is owned by Cisco now.... :-P

mohammed_moustafa Tue, 06/24/2008 - 23:08

Would you please send me a show interface output of an interface that is making troubles, for example if your Gig 0/1 is causing troubles excute show int g0/1 and please post the output.

kerryjcox Wed, 06/25/2008 - 13:31

Here's the deal. I have a Lenovo T61 Thinkpad. It has a built-in Intel 82566MM Gigabit network card. All the drivers are up-to-date.

It is plugged into a Linksys SD2008 8-port 10/100/1000 switch which then uplinks to the switch closet's Cisco 48-port 2950.

When I set network card for Auto-Detect, it defaults to 10 meg full. Nothing I do can get it to go higher than 10 megs.

When I hard code it to 100 meg full or auto-detect 1000meg, Windows XP says the network cable is unplugged. (No issues with my Fedora 9 Linux box or my CentOS 5 server that plugs into the same local Linksys switch.

Here is the output of Fa0/29 after clearing counters, which is what my Linksys switch uplinks to:

#sho interfaces fa0/29

FastEthernet0/29 is up, line protocol is up

Hardware is Fast Ethernet, address is 0011.bccf.201d (bia 0011.bccf.201d)

Description: S206-D-05 Data Cox

MTU 1500 bytes, BW 100000 Kbit, DLY 1000 usec,

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

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s

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

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

Last input 00:00:00, output 00:00:03, output hang never

Last clearing of "show interface" counters 00:09:54

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 output rate 0 bits/sec, 0 packets/sec

2482 packets input, 339472 bytes, 0 no buffer

Received 340 broadcasts, 0 runts, 0 giants, 0 throttles

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

0 watchdog, 325 multicast, 0 pause input

0 input packets with dribble condition detected

5664 packets output, 1362547 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 PAUSE output

0 output buffer failures, 0 output buffers swapped out

Not much to see there.

I have discovered others, including Mac users, are seeing the same thing. When we switch out their gigabit switches for smaller 10/100 Linksys switches, all their problems go away.

I am guessing the root cause is still Linksys and not Cisco, though Cisco should be smart enough to play nice with other network devices.

#sho ver

Cisco Internetwork Operating System Software

IOS (tm) C2950 Software (C2950-I6K2L2Q4-M), Version 12.1(12c)EA1a, RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2002 by cisco Systems, Inc.

Compiled Fri 27-Dec-02 10:46 by antonino

Image text-base: 0x80010000, data-base: 0x80664000

ROM: Bootstrap program is CALHOUN boot loader

MED-S4-2950-MDF uptime is 5 weeks, 5 days, 0 minutes

System returned to ROM by power-on

System image file is "flash:/c2950-i6k2l2q4-mz.121-12c.EA1a.bin"

cisco WS-C2950G-48-EI (RC32300) processor (revision P0) with 19968K bytes of memory.

Processor board ID FOC0839Z2AY

Last reset from system-reset

Running Enhanced Image

48 FastEthernet/IEEE 802.3 interface(s)

2 Gigabit Ethernet/IEEE 802.3 interface(s)

32K bytes of flash-simulated non-volatile configuration memory.

Base ethernet MAC Address: 00:11:BC:CF:20:00

Motherboard assembly number: 73-7409-12

Power supply part number: 34-0965-01

Motherboard serial number: FOC08391QSY

Power supply serial number: DAB0837GPJL

Model revision number: P0

Motherboard revision number: A0

Model number: WS-C2950G-48-EI

System serial number: FOC0839Z2AY

Configuration register is 0xF

glen.grant Wed, 06/25/2008 - 13:56

It could be a cabling issue , gigabit needs all 8 wires to be good to run gigabit. 10/100 only takes 2 pairs . Patch cables bad or incorrect or missing wires ???? These unmanaged switches need the connections to be set as auto ,anything else will probably cause problems.

kerryjcox Wed, 06/25/2008 - 14:01

Yes, I have considered that as well. We have tried various cables, some made and some purchased. All had the same result.

As these gigabit Linksys switches are unmanageable, there is not much we can do with them. And when we try manually setting the speeds on the Cisco 2950 ports, there is no effect.

So, yes, we already ruled out hardware to be the cause.

glen.grant Wed, 06/25/2008 - 14:07

Yeah the 2950 wouldn't have anything to do with the Linksys problems. Not sure what else you can try. Sometimes there are nic incompatibilities with certain equipment though I haven't seen one in quite awhile on actual cisco gear.


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