Jerry Ye Fri, 07/18/2008 - 07:59
User Badges:
  • Cisco Employee,

Have you check the port duplex setting? If it is Half Duplex, it will be a lots of collision. Bad media - port or cable, can cause a lot of collision also.



Richard Burts Fri, 07/18/2008 - 09:09
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN


The only way to fully avoid collisions is to operate the Ethernet in full duplex. There are no collisions in full duplex.

If you operate the Ethernet in half duplex there will be some collisions. Some collisions are normal in half duplex and are not a problem. What can be a problem is too many collisions. If you look at the total number of frames on the interface and look at the number of collisions you can get the ratio of collisions and that can help you to determine if you are having too many collisions.



vinothlb1 Sat, 07/19/2008 - 02:32
User Badges:

How to operate the ethernet in full duplex mode..

Marwan ALshawi Sat, 07/19/2008 - 03:51
User Badges:
  • Purple, 4500 points or more
  • Community Spotlight Award,

    Best Publication, December 2015

go to the interface config mode

interface e0/0

duplex full

rate if helps

Joseph W. Doherty Sat, 07/19/2008 - 04:31
User Badges:
  • Super Bronze, 10000 points or more

Some additional notes:

Not all devices support full duplex Ethernet, e.g. old equipment and 10 Mbps Ethernet.

Duplex mode, to work correctly, must be the same between the two devices.

Many newer Ethernet devices support an "auto" duplex mode, but it can sometime fail to function properly. It will also usually revert to half duplex expecially if the other side is configured "full" -- which causes very poor performance.

Valid duplex configuration combinations between devices are half-half, full-full or auto-auto. (Auto-auto usually should bring the two devices interfaces to full-full, but it might set them to half-half. The latter is less than optimal performance, but again, you don't want to see half-full, whether hard configured that way or set that way by auto-auto.)


This Discussion