VMware KVM madness

A couple weeks ago I set up two KVMs so that my work machine and personal machine could share my keyboard, mice (yes, I have one for each hand), audio, and monitors (I have three, but only two are shared). I bought two TrendNet KVMs, a TK-209 (for audio) and a TK-207 (for second mouse and monitor). Shortly I started experiencing problems where at random times, both KVMs would switch away from my work computer at the same time. To make it worse, sometimes when I tried to switch back (always using the buttons on the KVMs), the monitors would switch back but the mouse and keyboard would not work and the KVM lights would blink.

At first I just chalked this up to my bizarre setup. I figured 64-bit Windows XP might be to blame (who besides me uses that?) or the dual use of KVMs (but dual-monitor KVMs are crazy expensive!). But after a while I started to notice that there was a relationship with my use of VMware virtualization. So I finally did a search and found this forum entry which explained what’s going on.

It seems that in order to handle virtualization of the keyboard “lock” keys (caps lock, num lock, scroll lock), if there are any differences between how these keys are locked on the host and VM, VMware software resets all of them by virtually clicking them once or twice. Typically it’s the num lock that’s different, but the software just does all of them; in particular, switching between host and VM typically results in two scroll lock presses, which is the key combination that tells the KVM to switch hosts. Nasty! The simplest way to avoid it is just to make sure the settings match up between host and VMs.

Now that still doesn’t explain why both KVMs sometimes fail to switch back correctly; that perhaps is due to my unusual (and probably unsupported) setup. Rebooting the host does fix it, but I hate doing that. However I did have an episode today where eventually the KVMs righted themselves after waiting a while. So perhaps I will not send them back as I was starting to think I’d have to.

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One Response

  1. Something I figured out after a while to fix the situation where the KVMs fail to switch back:

    First of all, the KVMs actually switch the screens back fine. It’s the mouse and keyboard that don’t come back. But I have a separate keyboard attached to my main workstation and I can use this to get rid of any VMware VMs displayed on the screen (actually I have multiple desktops with Dexpot so I can just switch away to an empty desktop). Then when I switch back the KVMs they pick up the mouse/keyboard. It seems VMware is interfering with the re-attachment of the peripherals somehow.

    Anyway, my workaround is complete.

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