Review: Opengear 8-port Console Server

by Sandra Henry-Stocker

June 29, 2005 —

After writing a column two months ago about how wonderfully convenient it is to use console servers to manage otherwise "headless" servers -- and from as much distance as you care to put between yourself and the servers to be managed, I couldn't resist an opportunity to evaluate a line of console servers that cost less than half what the others that I've priced are selling for. And, given that I'm working in a lab that is already equipped with a number of console servers, I felt compelled to question, in addition to the things you'd expect me to evaluate -- such as how easily a unit is to configure and how reliable it is -- how much additional work would be involved in managing two competing brands of console servers in the same lab. After all, I have said numerous times that it's easier to manage three hundred systems that are all basically the same than half a dozen which are different. So, I had to consider whether the added burden of managing two sets of devices that provide the same basic service would outweigh the cost savings.

The Opengear CM4008

The 8-port console server from Opengear that I tested is a model CM4008. Unlike its rack-mountable big brothers (the 16- and 48-port units), this console server is very small -- only slightly larger than a NETGEAR 4-port hub -- and sits on small rubber feet.

The most complicated thing about conducting my evaluation turned out to be, not configuring the console server, but the cabling. Yet even this was not much of an issue. Basically, I had to be sure to use the two adaptors that were included in the box (rather than just any of the similar looking adaptors that I might find in the lab) to hook up my laptop to the box for its initial setup. For another, I eventually had to acquire some special serial cables (not all serial cables are alike) to connect the serial (i.e., console) ports on my servers. More on this in a moment.

The initial setup

Before I did anything else, I connected the cat 5 cable and the two RJ45-to-9-pin adaptors included in the Opengear package between the Opengear "local" port and the serial port on my laptop. Then, using Hyperterminal, I adjusted my com parameters to match those mentioned in the Opengear Quick Start Guide (8-N-1 and xon/xoff at 115200 baud) and logged right in to the CM4008 as root.

Once logged in, I then set an IP address, netmask, broadcast address and default router that would work with my local network. I did this using the ifconfig command; the Opengear CM4008, like the Cyclades console servers, uses an embedded Linux OS called Busybox. While Busybox may not include every one of your favorite Unix commands, it is reassuring to approach a brand new piece of networking equipment and find a familiar user environment. So, while logged in, I also had to check out ps -ef, netstat, grep, awk and several other basic Unix commands.

Once I got my Unix "fix", I returned to my desk, ready to start configuring the box using the web interface. This involved enabling and configuring the five ports that I would be using to provide console access to five Sun Fire V100s and adding myself as a user on some of these ports so that I could try accessing the remote consoles both as root and as a less privileged user.

If any of this sounds complicated, it wasn't. I just clicked on the Configuration link under the Serial menu label, logged in and then selected the settings I wanted from the pulldown menus. Since the defaults were nearly correct to begin with. I only changed flow control from hardware to xon/xoff and then activated telnet and ssh on the ports I wanted to use; the other settings were already set.

Cabling

Before hooking up to the console (serial port A) ports on my Sun Fire V100s, I had to come up with the right kind of serial cables. While the wiring of DB25 connectors for RS232 seems to have been carved in stone decades ago, the same is not true for RS232 connections using RJ45 jacks. These can be wired in any of several different ways. Fortunately, the pinouts on the Opengear box follow a popular wiring scheme and I was able to purchase some off-the-shelf cables intended for use with Cisco equipment for about $10 apiece. These cables arrived two days later. I considered building my own, but wasn't sure that I could tie ground lines and such together with the jacks that I had on hand.

The purchased cables were short, featured an RJ45 (male) plug on one end and an RJ45 (female) jack on the other. I used standard straight-through cat 5 cables (I have a file drawer full of these!) to extend the purchased cables to the lengths required to reach my five serial ports. By the time you read this review, similar cables may be available from Opengear as well.

Getting to my consoles

Once the servers were hooked up, I was able to connect first to the console server (where I logged in as myself or as root) and then to the V100 attached to the particular port.

The Opengear boxes automatically assigns a range of port addresses to the eight ports on the box. For example, with my Opengear console server set up as 10.10.5.25, I could address the console on port 1 by connecting to port 2001 on 10.10.5.25 (for telnet) or port 3001 on 10.10.5.25 (for ssh). Since I'm a PuTTY user, I saved each connection profile with the ports and one of my favorite color schemes to facilitate subsequent console access. Initially, I called these profiles "Opengear Port 1", "Opengear, Port 2" and so on. Soon afterwards, I renamed them after the attached servers and they had names like "Saturn Console" and "Pluto Console".

An interesting bonus that I hadn't anticipated was that I was able to connect to the console of any of my connected Sunfire V100 servers as many times as I cared to. In other words, each of my telnet and/or ssh sessions (as separately enabled via the web interface) to the same service port were connected to the same console session. If I typed the command "ps -ef", for example, I saw the issued command and its output on all connections. This feature provides a way to "share" the console -- an invaluable feature when one person is assisting another or helping to troubleshoot a problem on one of the connected systems.

Wrap up

All in all, I was delighted with the Opengear CM4008. For just under $500, this little box can give a sysadmin console access from home or from a hotel room or it can keep you at your desk and out of reach of those cold drafts that most computer rooms have that are so unpleasant for people. As for the alleged "added burden" of maintaining more than one variety of console servers in the same small lab, I didn't find there to be one. The Opengear is so straightforward to configure that the learning curve is practically non-existent.

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