Straight or Crossover are two methods of connecting the pins on RJ-45 Cat5 Network cables. There is no advantage or disadvantage (or the best) it must be connected right or the Network will not work.
The Rules of Connections for Hub, and or Switch are the same:
NIC to NIC - Crossover Cable.
NIC to Hub - Straight (regular) Cable
NIC to Uplink - Crossover Cable.
Hub (regular) to Hub (regular) - Crossover Cable.
Hub (regular) to Hub Uplink - Straight (regular) Cable.
Hub Uplink to Hub Uplink - Crossover Cable
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Cable/DSL entry on a Cable/DSL Router (WAN) is an Uplink connection.
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If your Modem came with Straight Cable:
Modem to NIC - Straight (regular) Cable
Modem to Hub - Crossover Cable.
Modem to Uplink - Straight (regular)Cable.
If your Modem Came with Crossover Cable:
Modem to NIC - Crossover Cable.
Modem to Hub - Straight (regular) Cable.
Modem to Uplink - Crossover Cable.
Unfortunately, there is no standard in Cable/Modem units, so the connection depends on how the manufacturer wired them.