how to tell if kernel XYZ supports IP aliasing?

From: Niall Mansfield (
Date: Wed Mar 05 2003 - 06:20:45 EST

Q1. Is there a definitive way to tell if a particular kernel
    supports IP aliasing?

I'm writing a tutorial on DNS that involves IP aliasing.
Most of the pre-packaged Debian kernels do support it, but
kernel-image-2.2.20-idepci 2.2.20-5 doesn't -- when you
        ifconfig eth0:1
it gives errors (on a laptop):
        SIOCSIFADDR: No such device
        SIOCSIFFLAGS: No such device

By downloading the Debian files you can eventually see, in
the kernel config file from the kernel-image tar file, that
        # CONFIG_IP_ALIAS is not set
But this is more than a newcomer to Linux could reasonably do; hence,
is there a definitive way for a newbie to see if
error messages are due to a kernel limitation rather than a mistake
on their part?

A related question:

Q2. In 2.2.x kernels, aliasing was compiled if CONFIG_IP_ALIAS is set.
    What controls this in new kernels where CONFIG_IP_ALIAS is
    no longer an option? (Or from some kernel version onwards
    has aliasing always been enabled?)

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