I use my Debian testing as a gateway, running dhcp service and ipmasq. But after a dist-upgrade today and reboot, I found I can not connect to the internet from this machine. My settings in network/interfaces seem to be no longer working, and strange addresses like 169.254.x.x are assigned to the two NICs. After two hours of searching and trying, I found the problem is network/if-up.d/zeroconf. Google told me that this thing is used to easy the connection between two machines, but actually it cracked down my gateway
I really don't know why debian somehow thought I need this package and installed it for me. Removing this package resolved the problem. And it didn't remove the file if-up.d/zeroconf, leaving it running with an error message. I deleted it myself.