ed0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        inet hidden netmask 0xfffffc00 broadcast hidden
        inet6 fe80::220:18ff:fe53:77ff%ed0 prefixlen 64 scopeid 0x1
        inet hidden netmask 0xfffffc00 broadcast hidden
        inet hidden netmask 0xfffffc00 broadcast hidden
        inet hidden netmask 0xfffffc00 broadcast hidden
        ether 00:20:18:53:77:ff

and i'm adding the following in rc.conf
ifconfig_ed0_alias3="inet hidden netmask 255.255.252.0"

those other aliases have been working for years i just need to add another one