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defferred counter on Catalyst 2900XL series switch

Cisco documentation indicates that "deferred frames" as shown when performing a "sho int" command are normal during ethernet operation. The documentation says that when "Carrier Sense" 1st listens to the wire and is busy, the frame has to be deferred.

Understanding that a switch port is its own collision domain, how can a "busy" ever be detected.

I have a customer who is having alot of deferred frames reported on their 2900XL switches. What can I do??...


  • Other Network Infrastructure Subjects
New Member

Re: defferred counter on Catalyst 2900XL series switch

This means that the switch sees the machine or network on that switchport is bussy so it has to wait until the network is free, if you have much deferred traffic, it would be wise to split up the connected network in to two or more smaller segments.


Re: defferred counter on Catalyst 2900XL series switch

Even in a switched environment where each switch port can be an individual collision domain you still have 2 users on each collision domain - the switch port and the user on the end of the port. As a result is the switch wishes to send a frame at the same time as the user is already sending (carrier has been ascerted) then the switch port will deffer it's transmission until the user has finished.

Please note though that this only applies to half duplex links, you do not get defers on a full duplex link as both devices can simultaniously send and receive. Therefore, if possible, try setting both devices to full duplex or if they have autonegotiated try hard setting the speed and duplex at both ends.

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