/etc/network/interfaces:

iface eth0:1 inet static
        up /root/test-ifup.sh $IFACE
        address 192.168.123.1
        netmask 255.255.255.0

/root/test-ifup.sh:

#!/bin/bash
echo $@

CLI:

# ifdown eth0:1 ; ifup eth0:1
eth0:1