Registered: Aug 2010
Location: Beaverton, Oregon, USA
Distribution: Pfsense, Ubuntu, Centos, Fedora, Redhat, Scientfic, MacOS
Here are some important features to look for:
1) KVM over IP (obviously)
2) Is the interface REALLY remote OS agnostic
3) How many admins may login simultaneously
4) Local console port in addition to via IP.
5) are multiple admins forced to share a system's screen?
6) if using usb on the system, can you virtualize a cdrom, or flash device?
7) Does the kvm use only analog cables, or some sort of cat-5 converter?
8) do multiple connections require a licence key?
9) does it have the ability to work with remote power control?
10) What is its power source? POE? Self-powered? Separate transformer?
11) are only ps/2 and usb ports supported? how about older sun systems, or serial consoles?
I have found each of the above a useful feature, and I will explain.
for #2, I have needed access to the datacenter from linux, windows, and even my personal macintosh system. This included via firefox, IE, and safari. I have even tunneled it over an ssh port-forward.
#3 is important because if I need access for an emergency, I don't want to be blocked by another admin that went to lunch. Perhaps a mechanism to break someone else's connection...
#4 because it's really nice to just walk up to a central keyboard and monitor in the server room, or somewhere else with a console extender. and in an emergency, you don't have to wait for your software to come up.
#5 is important because it allows others to work on their own.
#6 has saved my butt: I had to totally re-run a linux installation in Bangalore from the US, and I had the only media. It was slow, but I completed it during my working hours, and did not need to coordinate remote hands with the time zone differences.
For #7, I really like the devices that use cat5 to connect the kvm to the system via converter. It allows you to use your current network backplane to carry kvm signals. It is not networking however, so it still requires a point-to-point connection, but your cable lengths are extended to what cat5 can do.
I haven't run into #8 yet, and I hope I don't.
Numbers 9 and 10 I just added, but I haven't been concerned with these myself.
I can see number 11) being important, especially if you need the ability to connect to a serial console. However, if you need a lot of serial consoles, it may be better to acquire a serial server. I have used digi and cyclades with good results.
If you already have a kvm switch that doesn't have an ip interface, I recommend something like raritan's kxII-101 or Opengear's IP-kvm 1001 also looks good. This will allow you to leverage the basic kvm portion onto the network. For the rest of the features, YMMV.
It has been two years, but I have used raritan's dominion KX-II series: they passed everything above with decent colors. The kxII-101 is pretty much a single access device, thus failing #3, #4, and #5 above.
Raritan however is expensive. The sites kvm-switches.com has a vendor list. When I devote some time to looking for devices, I will go through this list.
A device I am interested in evaluating is opengear's ip-kvm 1001. It looks like it will daisy-chain with others, and apparently has the ability to have a modem connection.
I hope this helps...