Collisions occur if two nodes listen, hear nothing, and transmit simultaneously. This ruins both transmissions. There is a back-off algorithm that creates a random wait time for retransmission so that a second collision does not occur. MAC addresses consist of a 48-bit address expressed as 12 hexadecimal digits. Auto-negotiation has been known to fail.
Cisco recommends using static settings for important devices.
This technique minimizes the absorption of EMI from the surrounding environment. This helps reduce cross talk and nearby electrical noise. A straight through cable maintains the pin connection all the way through the cable. Thus, pin 1 is the same on both ends of the cable. Straight through cables are used to connect PCs or routers to hubs or switches.