Somebody has asked me about this.

I understand the application / use of RDNS for MX records and the like but I've never come across this for www records.

Quote:

...would implement a reverse lookup DNS entry for the web site. This would be used by systems that perform validation of URL's

Quote:

which could mean that some sites may not be able to access content on the MNL web site.

I've not come across anyone / thing that validates a URL via RDNS. Has anyone else?

Surely the theory falls down when you use host headers to host multiple WWW sites on one IP (as I thought you only had one RDNS entry for an IP)?

TIA,

Chris.

 

Yep, you can only do that with IP based virtual hosting. You can only have one PTR record per IP address, so with name based vhosting you can't check the reverse since it'll show a different FQDN.

 

Thanks Steven

So, if you are using one IP per website (very IP intensive and not something I'd want to do), does any product / thing / one do RDNS to validate a WWW record? I did think of caching or content filters but can't think what would be achieved from doing a RDNS lookup...

 

Can't think why it would give any benefit, don't know of anything offhand that does. Even for https-aware webservers (which require a seperate IP per certificate) there's no reason why a reverse lookup should return the FQDN of the site being browsed, the certificate is tied to the hostname.