Slow network speeds

Unanswered Question
May 7th, 2008

Just installed a 6509e and a 3560 switch in my LAN. Singlemode fiber is connecting the 2 switches using gbics. When moving data between the switches, transfer speeds get no higher than around 50mbps. Doing a sh int gig 5/1 produces the following. Lot of input errors. I would think possibly a duplex/speed mismatch, but it does not appear that I can configure on the sfp ports. Any help would be greatly appreciated.

GigabitEthernet5/1 is up, line protocol is up (connected)

Hardware is C6k 1000Mb 802.3, address is 0016.4708.9d30 (bia 0016.4708.9d3

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

reliability 254/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

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

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

Clock mode is auto

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

Last input 00:01:18, output 00:00:45, output hang never

Last clearing of "show interface" counters 01:10:38

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 0 bits/sec, 0 packets/sec

5 minute output rate 7000 bits/sec, 9 packets/sec

351983 packets input, 237817255 bytes, 0 no buffer

Received 123 broadcasts (91 multicasts)

158 runts, 0 giants, 0 throttles

830 input errors, 0 CRC, 672 frame, 0 overrun, 0 ignored

0 watchdog, 0 multicast, 0 pause input

0 input packets with dribble condition detected

415507 packets output, 438367084 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

I have this problem too.
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Paolo Bevilacqua Wed, 05/07/2008 - 15:07

Hi, you have some input errors, although not very many. You should look in having your fiber patch replaced.

vanguard1 Fri, 05/09/2008 - 12:02

I will have the fiber patch tested. Using ethernet backbone speeds were fine and no input errors. On the fiber port, after changing where I was plugged in on the panel, the times were better, but the input errors were still increasing. Link light was flashing green/orange indicating an error. Speeds were better, but would fluctuate.

donlerche Fri, 05/09/2008 - 10:54


You said you are using single mode fibre for the link, but the the show interface output states media type is SX - this indicates a multi mode transciever (If SFP/GBIC were single mode , then media type would be LX or LH). You cannot mix these modes unless using fibre mode conditioning patch leads. This may be your problem,

Hope this helps



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