Ifconfig with rc.conf Broken

[MC]

Bizarre behavior with configuring the main interface IP with rc.conf:

ifconfig_bge0="inet 10.0.0.15  netmask 0xffffff00"
ifconfig_bge0_alias0="inet 10.0.0.16 netmask 0xffffffff" # Sample alias entry.
defaultrouter="10.0.0.10"

Doesn't configure the bge0 interface!  But:

ifconfig bge0 10.0.0.8 netmask 0xffffffff alias

works fine in rc.local.  Also configuration from command line in
multiuser mode works fine, although I notice messages about bge0 going
down, then another about it coming back up upon adding the main IP

I apparently have identical behavior from another machine with an fxp0
interface, from 6.1-PRERELEASE cvsuped on Sunday