Below, in no particular order, are various tips I wish to dispense to the masses. If you choose to heed my advice and something breaks, you get to keep both pieces.
This info was incorrect; I will get around to fixing it someday.
There you have it: the world's shortest crossover cable. There is no trick here; just make a standard crossover cable (using the pinouts mentioned above) using as little cable between the plugs as possible. Then, throw the cable in your bag with a standard ethernet coupler (but make sure all 8 pins are present on each side of the ethernet coupler). This saves you from having to carry a separate normal crossover cable with you. Say you need a 100ft crossover cable temporarily: just attach a regular straight-through ethernet cable to your coupler, then the short crossover cable to your coupler, and you now have a 100ft crossover cable.
If you want to be really anal about specifications, make sure that each of the cable's pairs have at least one twist per pair (the one pictured above does).
This info was probably also incorrect; I will get around to fixing it someday.
Below
is a design for an ethernet cable continuity tester. You will need:
Jack #1 Jack #2 /-- Battery -- Pin 1 Pin 1 --\ | /-- Pin 2 Pin 2 --/ | \-- Pin 3 Pin 3 ----\ | /---- Pin 4 Pin 4 --\ | | | /-- Pin 5 Pin 5 --/ | | | \-- Pin 6 Pin 6 ----/ | \---- Pin 7 Pin 7 --\ \-- Light ---- Pin 8 Pin 8 --/
Basically, you are shorting certain pins on each jack, and attaching the battery and light to the first jack. Note that this configuration will not detect incorrect pin mappings, as nearly any cable configuration will eventually allow you to get from Pin 1 to Pin 8 on Jack #1. Instead, this would allow you to make sure that all wires in each plug are properly touching the pins in the plug. This can sometimes be a problem when you are crimping stranded cable.
As long as your cable is wired in the correct order, this continuity tester will loop through each wire in a normal straight-through, a 568A-568B crossover, or a gigabit crossover cable. It will also work with the loopback plug we made above.
More Photos
Why? They are in use everywhere. At work, we created our private network many moons ago, and used 192.168.0.0/24 as the data network, and 192.168.1.0/24 as the voice network. And we have been regretting it ever since. This becomes a problem when a user tries to VPN in from his/her Linksys/Netgear/whatever network, which is invariably numbered 192.168.0.0/24 or 192.168.1.0/24. Hello network overlap!
Instead, pick a random range in the RFC1918 space. There are 256 possible /24s in 192.168.0.0/16. 65,536 /24s in 10.0.0.0/8. Heck, most people overlook 172.16.0.0/12, that's 4096 /24s right there. The following private networks have been randomly generated, just for you:
Reload to get more random private networks. A web page to specify other IP ranges/netmasks is coming soon. In the mean time, if you know PHP and want to see the source to this page, it is available here.
