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Late Collissions - Ethernet 0 Interface 1721 Router

Hello ,

I have been observing high amount of Late Collisions on Ethernet 0 interface for a Cisco 1721 Router (LOL EOL for sure )

The internet line terminates on the interface

#sh int e0

6640 output errors, 5677 collisions, 0 interface resets

0 babbles, 6454 late collision, 10467 deferred

#sh controllers | i single

4304 single collisions, 1373 multiple collisions

For LAN Access ,the router has GRE IPSec Tunnels which forms EIGRP Neighborship with Remote end Router

Due to this issue , lately the GRE IPsec Tunnels flaps causing EIGRP Neighborship to get disrupted often resulting in connectivity loss

As late collssions can mostly be caused by Duplex mismatch , I checked the duplex settings and that seems to be fine

(https://supportforums.cisco.com/thread/9246)

1. The LAN has around 200 nodes connected via Fa0 intreface , Can the Speed mismatch ( 10Mbps and 100 Mbps ) cause bottle necks and be the reason for Late collissions ?

2. Are Late collissions bad ?

3. What are the options ahead of me to try and resolve this issue ?

Please Help !

Regards,
Anup

Regards,
Anup
1 ACCEPTED SOLUTION

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Hall of Fame Community Legend

Can the Speed mismatch ( 10Mbps and 100 Mbps ) cause bottle necks and be the reason for Late collissions ?

No.  Speed mismatch gives you CRC or FCS.  Collisions, as a whole, means you're interface is set up for HALF duplex.

Post the complete output to the command "sh interface ".

Ethernet0?  I believe this interface can only negotiate HALF duplex. 

View solution in original post

3 REPLIES 3
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Hall of Fame Community Legend

Can the Speed mismatch ( 10Mbps and 100 Mbps ) cause bottle necks and be the reason for Late collissions ?

No.  Speed mismatch gives you CRC or FCS.  Collisions, as a whole, means you're interface is set up for HALF duplex.

Post the complete output to the command "sh interface ".

Ethernet0?  I believe this interface can only negotiate HALF duplex. 

View solution in original post

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Hall of Fame Community Legend

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Hi Leo ,

It 's Half Duplex itself !

Sorry I checked the Fa0 port and found it to be Full Duplex

For E0

Ethernet0 is up, line protocol is up

  Hardware is PQUICC Ethernet, address is 000d.28db.6d26 (bia 000d.28db.6d26)

  Description: == Public IP ==

  Internet address is 1.2.3.4/24

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

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

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Half-duplex, 10BaseT

  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: 0/75/351/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 3000 bits/sec, 3 packets/sec

  5 minute output rate 3000 bits/sec, 3 packets/sec

     3962930 packets input, 1547443857 bytes, 640 no buffer

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

     6677 input errors, 0 CRC, 0 frame, 5 overrun, 6666 ignored

     0 input packets with dribble condition detected

     5588762 packets output, 1453864156 bytes, 0 underruns

     6666 output errors, 5697 collisions, 0 interface resets

     0 babbles, 6480 late collision, 10494 deferred

     186 lost carrier, 0 no carrier

     0 output buffer failures, 0 output buffers swapped out

Regards,
Anup

Regards,
Anup
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