02-27-2007 09:01 AM - edited 03-05-2019 02:36 PM
I'm getting a lot of late collisions on the WAN side of my router (Cisco 2801.) In the log I am also seeing errors every few minutes where that interface will come back up. I am having throughput issues with this router and I think this may be a duplex mismatch. Does this sound right?
02-27-2007 09:20 AM
Can you provide the "show interface" output of the interfaces on both side of the WAN link ?
02-27-2007 09:23 AM
rtr#sh int
FastEthernet0/0 is up, line protocol is up
Hardware is Gt96k FE, address is 0019.2fa4.38f8 (bia 0019.2fa4.38f8)
Description: $ETH-LAN$$ETH-SW-LAUNCH$$INTF-INFO-FE 0$$ES_LAN$$FW_INSIDE$
Internet address is 10.10.10.1/24
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, 100BaseTX/FX
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 1/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 4000 bits/sec, 3 packets/sec
5 minute output rate 2000 bits/sec, 2 packets/sec
15086034 packets input, 88230789 bytes
Received 4353489 broadcasts, 0 runts, 0 giants, 0 throttles
2 input errors, 0 CRC, 0 frame, 1 overrun, 0 ignored
0 watchdog
0 input packets with dribble condition detected
11475289 packets output, 3392575167 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
FastEthernet0/1 is up, line protocol is up
Hardware is Gt96k FE, address is 0019.2fa4.38f9 (bia 0019.2fa4.38f9)
Description: $ES_WAN$$FW_OUTSIDE$$ETH-WAN$
Internet address is 66.101.199.34/30
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half-duplex, 100Mb/s, 100BaseTX/FX
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/39/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 9000 bits/sec, 14 packets/sec
5 minute output rate 3000 bits/sec, 3 packets/sec
29679920 packets input, 335398060 bytes
Received 18194333 broadcasts, 0 runts, 0 giants, 0 throttles
2 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog
0 input packets with dribble condition detected
11108075 packets output, 3375348659 bytes, 0 underruns
27501 output errors, 22690 collisions, 26708 interface resets
0 babbles, 27613 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
NVI0 is up, line protocol is up
Hardware is NVI
MTU 1514 bytes, BW 10000000 Kbit, DLY 0 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation UNKNOWN, loopback not set
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
rtr#
02-27-2007 09:25 AM
that is correct Late Collisions are generally caused by a duplex mismatch
02-27-2007 09:33 AM
Your WAN FE interface is working as 100MB half duplex, that's why you are getting a lots of late collisions and output errors. Please check the duplex part on the other side and match it. It should be fine after the settings are same at both the sides.
-amit singh
02-27-2007 09:36 AM
Looks like fa0/1 is 100mbps half duplex - You might check the other end and you'll most likely find it at full duplex.
Hope this helps
02-27-2007 01:48 PM
Yep - was able to force it to Full Duplex/100Mbps and the late collisions have stopped. Thanks for the feedback.
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