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Beginner

lot of underruns and buffer failures in fasteth interfaces

Hi,

I have some problem with a 3548XL switch in fastethernet interfaces.

I see a lot of "underruns" in output packet and a lot "buffer failure" in all interfaces, for example

FastEthernet0/45 is up, line protocol is up

Hardware is Fast Ethernet, address is 0004.9b57.886d (bia 0004.9b57.886d)

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

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

Encapsulation ARPA, loopback not set

Keepalive not set

Auto-duplex (Full), Auto Speed (100), 100BaseTX/FX

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

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

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

5 minute input rate 330000 bits/sec, 303 packets/sec

5 minute output rate 439000 bits/sec, 337 packets/sec

2294047587 packets input, 2488211861 bytes

Received 140718 broadcasts, 0 runts, 0 giants, 0 throttles

1 input errors, 1 CRC, 0 frame, 35 overrun, 35 ignored

0 watchdog, 0 multicast

0 input packets with dribble condition detected

2544049878 packets output, 2343816642 bytes, 632503 underruns

0 output errors, 0 collisions, 1 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

632503 output buffer failures, 0 output buffers swapped out

Can we resolve the problem?!

Thanks a lot in advance

Cinzia

6 REPLIES 6
Highlighted
Enthusiast

Re: lot of underruns and buffer failures in fasteth interfaces

Since you auto-negotiated to 100/Full try setting the speed and duplex on the interface and force them to 100/Full. Then recycle the interface (shut/no shut)....

Highlighted
Beginner

Re: lot of underruns and buffer failures in fasteth interfaces

I cannot do it, because I cannot set speed and duplex on the server connected to this interface.

This problem is present only for this switch, there are 12 switches on the net, and only on a limited number of interfaces I have configured speed and duplex, but the problem is only for that switch.

Thank you

Cinzia

Enthusiast

Re: lot of underruns and buffer failures in fasteth interfaces

Cinzia,

An underrun is when the transmitter runs at a higher rate than the packets sent to the hardware buffer. This is when the packets are going out faster than the hardware buffer can send them, just the opposite of an overrun.

Can you provide output of the "show buffers" command?

If you have access to CCO you can use output interpreter to run analysis on your buffers.

Does this switch serve an other purpose opposed to the others in your networ. I.e. does it house servers or is it an distribution point of any kind? That is interesting to know.

HTH

--Leon

* Please rate ALL posts.

Highlighted
Beginner

Re: lot of underruns and buffer failures in fasteth interfaces

Hi Leon,

the analysis of the output interpreter seems not show particular error, I attach the file of "show buffer" and "show controller eth".

Thanks a lot

Cinzia

Highlighted
Enthusiast

Re: lot of underruns and buffer failures in fasteth interfaces

I have seen issues where the interface auto negotiates a speed and duplex however it needs o be forced at a speed and duplex. Try forcing the switch interface to 100/full and reset the counters and see what happens. It is useally the NIC driver on the server that causes this issue. I noticed this on SUN servers. Give it a shot and see what happens....

Highlighted
Beginner

Re: lot of underruns and buffer failures in fasteth interfaces

I have moved the server to another similar switch, and I don't have any problem now, without set duplex and speed.

I think the problem is into the switch but I cannot understand why....

Best Regards

Cinzia

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