[CentOS] Hidden networking device configuration

I am trying to configure load balancing for a couple of CentOS4 servers.
In order to make it work, I need to add a hidden networking device on
each server with the virtual IP.  I found the following instructions on
linuxvirtualserver.org for doing this, but they don't work.

    echo 1 > /proc/sys/net/ipv4/ip_forward
    ifconfig dummy0 0.0.0.0 up
    echo 1 > /proc/sys/net/ipv4/conf/all/hidden
    echo 1 > /proc/sys/net/ipv4/conf/dummy0/hidden
    ifconfig dummy0:0 172.26.20.110 up

When I try to write to /proc/sys/net/ipv4/conf/all/hidden, the system
refuses to let me create the file.  I'm logged in as root, so why am I
having permission problems?

Also, I believe these instructions are for 2.2 or 2.4 kernels.  Have things
changed with 2.6?

-- 
Bowie