Multiple interface aliases - entire subnet

[arkade]

Hi,
I'm wondering if its possble to alias an entire subnet in one hit rather than doing individual IP's with:

ifconfig eth0:1 1.2.3.4
ifconfig eth0:2 1.2.3.5
.
ifconfig eth0:50 1.2.3.54

I'm wanting to alias an entire /21 subnet so doing it this way isnt practical and maybe not even possible (is there a limit on how many aliases you can have?).

I thought maybe this is possible with ip route or similar.

Any help would be appreciated,
Rob.

[arkade]

#! /bin/bash

for NUM in $(seq 1 255);
do
ip addr add 1.2.3.$NUM/21 broadcast + dev eth0
done

Nest for loops for modifying the preceding octets