cannot use IP to install OS over http

[Aldo Foot]

I was doing a Linux install over HTTP.
When asked to enter the HTTP server host  identification I chose to give
the IP rather than the FQDN, which resulted in an error halting the install.
The problem is fixed by giving the FQDN of the host rather than the IP.

The part of interest is the  [id "960017"] in the /var/log/httpd/error_log.

[Thu Sep 18 13:25:28 2008] [error] [client xxx.xxx.xxx.xxx]
ModSecurity: Access \
denied with code 400 (phase 2). Pattern match "^[\\\\d\\\\.]+$" at \
REQUEST_HEADERS:Host. [id "960017"] [msg "Host header is a numeric \
IP address"] [severity "CRITICAL"] [hostname "xxx.xxx.xxx.xxx"] \
[uri "/inst/disc1/images/stage2.img"] [unique_id "vQ66SI-onWgAAFVnrkUAAAAH"]

I use the error id to locate a line in the config file
         /etc/httpd/modsecurity.d/modsecurity_crs_21_protocol_anomalies.conf
which prevents the use of IP address in the above scenario:
I guess the problem is eliminated by commenting the line out.

Is there a better solution?
Why is using the IP a problem as indicated earlier?

~af