Lion doesn't wait for DHCPACK on wifi after resume?

Question

I've been noticing this occasionally on my MBA, and just got asked about it by someone else who's also seeing it:  when resuming Lion with a WiFi connection, sometimes it will bring the network up for a couple seconds, then drop for a bit with the WiFi icon showing it requesting an IP address, then come back.  HardwareGrowler shows it initially coming up with the same address it had been using when suspended, then eventually getting a new address, which leads me to believe that Lion is speculatively bringing up the interface on the old address without waiting for a DHCPACK; if it gets DHCPNAK instead, it then has to take the interface back down and go through the usual DHCPREQUEST/DHCPOFFER dialog with the DHCP server.
Is there a way to make it wait until it has received a reliable address (either DHCPACK to the old lease or the full DHCP negotiation) before bringing the interface up, rather than having it "stutter" when the original lease isn't ACKed?
FWIW I have seen this with all versions of Lion.  I don't recall seeing it with older versions.

Answer 1

NOTE:  I did exactly what you want to do all the time, and it works very well.  BUT I have set things up so that this works.
Do both WiFi and Ethernet get the same IP address from your router?  If not, then your existing file sharing setup is already established over the IP address assocaited with WiFi and that is where your transfer is going to stay.
Again, if you are currently getting different IP addresses, then I see 2 approaches
a) If your router's DHCP server allows associating an IP address with either a system's MAC address (Media Access Control; looks like nn:nn:nn:nn:nn:nn), or by associating an IP address with the "DHCP Client ID" (See System Preferences -> Network -> Advanced -> TCP/IP -> DHCP -> DHCP Client ID), then configure your router so that both the WiFi and Ethernet are connections to the router are assigned the same IP address.
b) another approach is to change each Mac's network setup so that they used Fixed IP addresses when at home (you can create a new network location for home use).  You would configure the WiFi and Ethernet interfaces so they have the same IP address (each Mac gets its own unique IP address, and if possible the address you assign should be outside the router's DHCP address range, so that the router does not assign a duplicate address).
If both interfaces have the same IP address, then when you plug in the Ethernet cable (assuming the interface order has Ethernet as higher than WiFi - which is the default)