defered counter increaseing on a ethernet port

[rfuchser]

Hello

we have a switch Catalyst 3524-XL-EN which is connected to a Cisco 827 ADSL router. This router has a 10Mb Ethernet port. So far we configured the port (0/1) where the router is connected to speed =10Mb and duplex = half. If I do a sh int after some period I can find a increased counter of deferred. Is this a normal behaviour on a half duplex Ethernet? In the command reference

I couldn’t find some detailed information how it’s exactly work.

FastEthernet0/1 is up, line protocol is up

Hardware is Fast Ethernet, address is 0007.0eee.6241 (bia 0007.0eee.6241)

Description: to router r_lachauxd_1

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

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

Encapsulation ARPA, loopback not set

Keepalive not set

Half-duplex, 10Mb/s, 100BaseTX/FX

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

Last input 00:00:32, output 00:00:01, output hang never

Last clearing of "show interface" counters 3d01h

Queueing strategy: fifo

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

5 minute input rate 2000 bits/sec, 1 packets/sec

5 minute output rate 2000 bits/sec, 2 packets/sec

473887 packets input, 155900469 bytes

Received 8009 broadcasts, 0 runts, 0 giants, 0 throttles

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

0 watchdog, 4423 multicast

0 input packets with dribble condition detected

566129 packets output, 92325959 bytes, 0 underruns

0 output errors, 264 collisions, 0 interface resets

0 babbles, 0 late collision, 307 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Thanks for any help

Rolf

[Erick Bergquist]

From Cisco:

http://www.cisco.com/en/US/tech/tk389/tk214/technologies_tech_note09186a008009446d.shtml#deferred

The deferred counter counts the number of times the interface has tried to send a frame, but found the carrier busy at the first attempt (Carrier Sense). This does not constitute a problem, and is part of normal Ethernet operation.

Probably what is happening in your case is , users on 3524 are all trying to go out ADSL connection to internet thus large amount of traffic. 307 deferred packets for 3days isn't bad. I've seen the deferred counter go up by hundreds in a minutes time, thats when you have a problem.

Possible solutions / workarounds: On switch, make sure all devices are same speed/duplex therefore less chance of bottleneck causing defers (100meg to 10meg, etc). Remove/replace slow devices.