It looks like the networking rewrite in Vista took out an old (hacky via registry) feature that allowed Windows to do what any other OS allows, assignment of a secondary static IP to a network interface with an active DHCP IP.

Anyone know a way to still do this under Windows 7? My situation is that I want to configure Synergy between my Mac and PC with a static IP to avoid issues with my DHCP IP changing. The DNS servers here aren't the quickest things to update (my IP change from friday still isn't showing up properly), so I figure just hardcoding IPs for Synergy will be the most reliable setup.

Keep in mind the "Alternate Configuration" tab that shows up in the TCP/IP properties is only for setting what IP is used when a DHCP server is unavailable. It isn't for having both a static and DHCP IP active at the same time.

I had, in the past, used that "Alternate Configuration" tab for the very thing you want to use it for: Simultaneous DHCP and fixed addressing. Are you *certain* that it doesn't work for your purposes now?

Does win7 permit doing this with an ifconfig command?

Eg. (Linux example):

ifconfig eth0:1 10.1.0.5

Yep. They fixed the "bug" where the Alternate Configuration was active when the primary configuration was talking to a DHCP server. The machine failed to ping it's own alternate config IP when I tried that.


Nope. It does have something similar now, but if I try and use the add command on the existing interface, it shuts off DHCP and uses my config as the primary. Subsequent add commands then properly add the additional IPs to the interface. It doesn't appear to support the :1 nomenclature that Linux uses.

The Windows 7 command is "netsh interface ipv4 add address"

Damn. Blast.

Any idea which version of Windows that happened in, just in case I ever run into a situation where I need to use the unrepaired version of windows to perform that trick?

Vista changed it, probably with the entire network rewrite that came in that dropped the tried and true evolved BSD networking code for internal Microsoft crap. One of the reasons Vista was on my do not use list, the network stack just did some stupid things when it was in a mixed network environment. The paid service pack to Vista seems to have helped quite a bit, but it's still not back to where it was in XP.

*edit* Gah, keep forgetting the BSD TCP/IP pieces were only in until NT 3.5 timeframe, back when the network stack was licensed after the OS/2 divorce with IBM. Anyhow, still a lot of issues came in when MS rewrote it for Vista.

Are there not, other ways to get a vista system to believe packets destined for some other IP should be accepted instead.

I don't think so.

Windows server will do all that using its own router features, including, i believe, multiple IPs on one NIC.