Cisco Console Cables, aka AUX cables

Cisco guide to console cables.

Cisco is legendary for these. While they are not strictly required, they are your only way out if you screw up your configuration and lock yourself out of your router.

I used to build these by hand, to save money, but lately, I've seen them on sale on ebay and Amazon for around $5 with shipping included. So I don't bother building them anymore. What's probably happened is there's a huge overstock of cables with 9-pin ports at one end, and laptops no longer have those 9-pin ports. So, to use these, you will also need a USB-to-9-pin-RS-232 adapter.

You can even get these with the RS-232 adapter right on the cable. They cost around $30... which is pretty expensive. The regular USB-to-serial adapters are $10 to $15. A really good one is the Keyspan, which costs $30.

There are some adapters out there that will turn Cat5 Ethernet cable into a Cisco console cable.

Newer Cisco equipment (post 2010) may have USB console ports. Too bad it requires a driver :( The appeal of the console cable is that you can use any computer with it.