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Excessive Late Collisions

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lardum

IS-IT--Management
Apr 26, 2000
462
SE
I'm experiencing a lot of Excessive Late Collisions on only one interface all the time. This is connected to a Cisco firewall. Anyone have any ideas why?
 
A local collision occurs when two or more nodes transmit at the same time. If two nodes collide on the other side of a repeater, the instrument counts this as a Remote Collision. Local Collisions and Remote Collisions are only reported at 10 Mbps.

On a 10BASE-T network, Excessive collisions are most often caused by a physical media problem such as missing or incorrect terminators, impedance discontinues (such as, defective connecters, cable stubs, crushed cables), or defective network interface cards.

In other words, I suspect that you have a 10Mbps hub in the middlw or replace the cable.

Hope this helps.
 
No, we don't have any 10BaseT equipment.

From my HP 4108 switch with only 10/100/1000Mbit/s ports one port is connected to a Cisco Firewall. The firewall is set to run 100Mbit/s full duplex. And also the HP port.
 
If the HP port really was configured for 100full it wouldn't report collisions, since they are not possible on a full duplex link. Late collisions on a switched TP link can only occur if there is a duplex mismatch, i.e. one side runs half duplex, the other side runs full duplex.

Please double check, that both ends of the link are configured for *fixed* 100Mbit/s full duplex and auto-negotiation is disabled.

In general, I think it's better to try *both* sides set to auto-negotiation first. Only in case this fails set *both* sides to the *same* fixed settings.

*Rob
 
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