Terminal servers -- saving your bacon, one console at a time

Serial terminal servers are dirt cheap and let you tap remotely into the consoles of a range of devices

Sometimes a simple piece of hardware or software -- and the presence of mind to install it -- can make all the difference in the world when the walls come crashing down. One of these items is the oft-ignored serial terminal server. In fact, I'd wager that many IT professionals don't even know what one is offhand.

I genuinely miss the Cisco 2511 terminal server. Outfitted with a couple of octopus cables, it was a trusty Swiss Army Knife during the golden age of the Internet.

[ As this networking Deep Dive attests, InfoWorld contributing editor Paul Venezia is a veritable font of network wisdom | Also see Matt Prigge and Paul Venezia's "10 tips for boosting network performance." ]

I've used 2511s to run modems in the days when 33.6kbps was warp speed. I've used them as routers, and I've used them as, well, terminal servers and connected those cables to the serial consoles of other network devices, servers, and whatnot. They've long since gone end-of-life -- but there are plenty of alternatives on the market. In fact, you can pick up used 16-port serial terminal servers from Avocent (who bought Cyclades four years ago) or Perle for as little as a few hundred dollars, depending on port count.

That $200 can easily be the difference between a ruined weekend and a nonissue. Sometimes, it can turn a potentially a massive and prolonged outage into a blip on the radar. And terminal servers aren't just for network devices.

In many cases, you can configure server hardware to ignore the framebuffer and output straight to serial. As long as you're not running a graphical operating system, you can do everything you want to a server from a standard serial connection, from BIOS modifications to rescue booting to full-on administration. If you're running a GUI, you can at least get to the BIOS out of the box.

A serial console connection is also generally faster than KVM-over-IP or an ILO remote console session. It's also much more robust over high-latency and low-bandwidth links, which means you're more likely to be able to fix a problem from your cell phone over a serial console session than via any other method.

All network hardware and a wide variety of other devices like storage arrays, blade chassis, UPS systems, and even air conditioning units have a serial console. In most cases, it's as simple as plugging in a cable -- voila, instant out-of-band management access to that device as long as it has power.

Also, most terminal servers support analog modems or come with an internal analog modem; even if all hell breaks loose and the network goes down, you can still gain access to the very components needed to bring that access back. It's the best way to ensure that your infrastructure can be fixed during planned or unplanned downtime -- short of setting up cots and a hotplate in the server room.

A serial terminal server of sufficient size should be part of every IT infrastructure, but it's especially useful for unattended remote sites. It shouldn't even be a question -- it should be mandatory, right along with a locking rack or server room and environmental monitors.

That said, I'm always dismayed when I see a data center wholly lacking in serial console connections. These ports exist for a reason, and not taking advantage of them -- especially when it's so cheap to do so -- is perplexing at best. Even if you buy brand-spanking-new terminal servers, they're still not terribly expensive and offer plenty of bang for the buck.

To some, it may seem odd that I'm singing the praises of one of the oldest forms of computer communication: the lowly serial port. Why bother with such Paleolithic technology when we have all kinds of bandwidth, redundant this and that, and disaster recovery plans sitting on the bookshelf?

Because there are guaranteed to be occasions when having a remotely accessible 9600/8-N-1 serial connection to a piece of IT gear saves mountains of time, effort, and headaches on everyone's part -- and that should be all the justification necessary.

This story, "Terminal servers -- saving your bacon, one console at a time," was originally published at InfoWorld.com. Read more of Paul Venezia's The Deep End blog at InfoWorld.com.

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