I have a bet going for $1 with a co-worker that traffic from two subnets on the same transport of Cat 5e cable eat bandwidth up from the other... He believes that because they are on two separate subnets 255.255.255.0 and 255.0.0.0 that there is no interacton between the packets on the different subnets.

Haven't found anything online to prove either way. He thinks that both subnets will have full bandwidth and not +/- 50% PER subnet if both are full of traffic at the same time.

Due to electrophysics I would believe that they would affect each others bandwidth on the same cable that is shared between the two since the NICs are transmitting the packets on the same frequency and not separate channels on the cable.

Who is correct me or him and can you provide a link to the fact ... Its only $1 bet, but I am sure he will want to see the proof...

Thanks .... Dave Carrier sense multiple access(Click)Thanks Raptor !

Knew the answer was out there and someone here could help...

DaveGuess you should have raised the stakes. Transmission on an Ethernet cable cat 5e is full duplex. 1 pair is used for sending, one pair is used for receiving (in case of Gigabyt Ethernet we talk about 2 pairs for sending, 2 pairs for receiving). There is discussion between the use of hubs and switches, collission domains.

Of course that one transmission "affects" the other, each "eats" as much bandwidth as disponible. It is used the same SIGNAL, but with different identification patterns. There are the same signal characteristics for both networks, the single THING that is changed is the destination address. There is a problem with the quantity of data transmitted on the wire (and you can ask your mate about congestion, for example), but this is sensed in the switch/hub, the data is not sent on wire where it will cause a collision. The "collision" is detected in the switch/hub, and consist of too many packets sent to one device in a too short time. Each device has its limit to send data, each device can compute a certain number of packets per second. Give to it more, and here you have the congestion. Let's say there is an auto route, that allows 50 cars per minut, at a MAXIMUM SPEED of 50 kmph. If there are 60 cars per minut, you have congestion. The speed limit remains. There is no collission, there is only congestion.

CSMA/CD principles are applied in wireless networks, in shared media. If we have no shared media... No shared media, no collission and no collission detection.

You are right.