Duplicate IPs, ZeroTier and ArpRetryCount

I’ve been experimenting with ZeroTier as a simple to set up VPN alternative and it’s been a relatively smooth experience so far. I won’t go into much detail here, but I can definitely recommend giving it a go for people working remotely. It’s not a complete replacement for VPN of course, but is very easy to set up, offers good performance and little administrative overhead.

With one Windows client however, I experience a strange issue: Windows kept insisting on assigning an Autoconfiguration IP to the virtual network adapter created by ZeroTier, in addition to the actually assigned ZeroTier IPs. The ZeroTier IPs would show up as “19x.x.x. (Duplicate)” while the former would show as “169.254.x.x (Preferred”). Obviously we do not prefer this one at all.

The solution at least for me was two-fold. First, turn off auto configuration. This is not a big loss, imho, since I can’t remember ever having to rely on some auto configured IP at all.

Fire up the registry editor and change (or add the REG_DWORD key, if it does not exist):

Restart Windows.

Profit.

(Note that theoretically setting the ArpRetryCount to 0 could cause issues if you are dealing with duplicate IPs in your network a lot (if people manually assign IPs to their machines randomly). Since ideally you should use DHCP anyway, that should not be an issue.)

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