Routers, wireless access point Ethernet ports, and PC NICs all send using pins 1 and 2, whereas hubs and switches send using pins 3 and 6. Straight-through cables are used when connecting devices that use the opposite pairs of pins to transmit data (Tx to Rx and Rx to Tx), if the devices are the same (use the same pins for Tx and Rx) then we must use a cross-over cable to cross the transmission.
No, for instance pc-to-pc Ethernet RJ-45 would normally use x-over. Answer really depends on whether the port is MDI or MDI-X. Some older network devices might have two physical jacks for the port (MDI and MDI-X), dedicated uplink port, or method to configure MDI or MDI-X for the port. Some of the latest devices will auto configure themselves. More info in this Wiki article: http://en.wikipedia.org/wiki/Medium_dependent_interface
When things are "normal' use a straight through, when things are the same, or occupy the same place connecting to a device (like a router and a PC would both connect to a switch), then use a crossover.
For nearly every test, console cables are "rolled" (also usually described as DB9 and rolled cable)
One more time ... try this inter-networking guide. It's an online version of Cisco Inter-networking Guide, a large and expensive book, but the online version is free.
It can be searched, it answers a lot of questions ... give it a shot.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...