I've put together a small kit, which can give me quick access to the serial consoles of various machines, for those little emergency trips to the colocation facility, or a customer site. It's been so successful and handy that colleagues are borrowing it for small cluster jumpstarts, and even for a Disaster Recovery exercise. So, I'd also describe it here.
The gist is, I started with a small 8-port console server, so I could use my laptop, a pre-configured telnet client, a crossover-Ethernet cable, and a handful of adapters to connect to various devices. I found that I often needed to be connected to the machine's network as well, so I added a small hub to the kit, as well as a small power outlet strip to my laptop bag.
I picked the Cyclades TS-800 8-port console server because it was small, was BREAK-safe, and ran from a 'wall wart' (power pack). I really wanted one that could run on 12-volts DC, so I could run the kit on car battery power, but couldn't find one. My laptop can also run from 12-volts DC (which could be handy in an emergency). Sadly, the TS-800 units are no longer sold by Avocent, but there are still a variety of small console servers on the market.
The small console server fit in the large pocket of my laptop bag, but limited how many cables I could carry, along with all the adapters. I finally fell to using a small, extra bag for the console bits.
I added a small 10-Mbps hub initially, so I could also do some packet sniffing, since most small switches don't have the ability to 'span' or 'mirror' ports. But, that bottleneck also throttled network access to the attached device, and I wasn't doing so much packet sniffing, so I 'traded up' to a Allied Telesyn AT-FS708LE 8-port 10/100 Mbps switch. This is a 12-volt DC device. It's small, lightweight, sturdy, and still available cheaply.
The kit now includes the switch, the console server, two crossover-Ethernet cables (1'- and 5'-long), an assortment of lengths of regular 8-wire CAT-5 cables, and an assortment of 24 Cyclades serial adapters. I also have a few 1'-long Cyclades null-modem (DCE-to-DTE crossed RJ-45 cables, and a few CAT-5e-rated female RF45 couplers. Add in the wall warts, and the kit lives in a 6-quart Sterilite plastic container about the size of a shoebox. Easy for security folks to see what is inside, but you don't want to put this in the belly of an airplane.
The Console Server is really the key to this kit, so here's what I've done to make it work;
First, configured the device as a console server, then copied the config file so I have an on-board copy, in case someone feels the need to change settings while they borrow it.
cp /etc/portslave/pslave.conf /etc/portslave/pslave.bkup
Make sure the backup config is saved into the unit's NVRAM. On the Cyclades, this means adding the file into /etc/config_files. (This is one reason I strip most of the comments out of my console server config files, since I'm basically saving two copies of the configuration file.) Now, if someone needs to change the config file, it's quick and easy to get back on the console, and copy the config back over the pslave.conf file, then 'saveconf' and reboot.
I also add an entry for my laptop into the /etc/hosts file on the console server, to reduce delays when making your reverse-TCP connections to the console server.
I had originally assigned different port speeds (19.2k, 38.8, 57.6, and 115.2) to ports 5 through 8, to make it quick and easy to access a high-speed port. But, I found that most ports are STILL at 9.6kbps as a default, and sometimes I needed more than 4 ports. In those cases when I needed a higher speed, I often needed more than one port at the higher speed at the same time. Since I found myself making many configuration changes I decided to revert the base configuration to 9.6k all 'round, but that's just explaining my reasons. You may want to do it your own way, and that's up to you.
I also pointed all the "extra" services (Radius server, syslog, etc) that the console server might want to use to the laptop IP address. I already use a small but of RFC-1918 address space, to reduce the chances of a conflict with the network that I may attach to. Pointing just to my laptop reduces the chance of the TS tripping any Intrusion Detection System (IDS) that might be watching the network. (I don't use the Syslog much anymore, but if I want to try it, that's one less part I need to configure.)
The current laptop is a PC, using PuTTY as the client tool. This lets me save the basic settings for "ts-1" through "ts-8" (configured to connect to the IP address of the console server, at ports 7001-7008, respectively). I use a distinctive window size and text/background colors for these windows, and each connection is configured with a unique 'window name', and a unique log-file name. The distinctive window settings make it easy to tell which open windows are serial connections, versus network sessions when I'm debugging.
An advantage to using PuTTY for this, is I can also 'export' a copy the Windows Registry settings for these sessions onto my FLASH fob, and easily give the settings to someone who is going to borrow the kit, and VIOLA! They are ready to connect to the ports quickly and easily. PuTTY is small, and runs without needing to be 'installed', so I have a copy of that on the FLASH fob as well.
The final bit that makes the kit as easy to loan as it is for me to use it, is a 1-page README document (also on the FLASH fob...with a canned Conserver config snippet for this device, just in case), which outlines the default IP settings, serial speed settings, adapter and cabling clues, and basics about how to open a reverse-TCP session to a serial port. I also include clues and the password for configuring the device. (Add a few useful labels to the hub and console server, mark the wall-wart connectors with a color-code at the device-end, and things go pretty smoothly.)
I don't use it very often, but when I need it, it's ready to go! When your time is worth money, having a kit on the shelf is money well spent!