Search Again: Re: more than one name for an IP address From: Global Homes Webmaster Date: Wednesday, May 17, 2000 Time: 1:50:30 pm On 05/17/00 at 13:18, Systems wrote: > Question: > > Another ISP is hosting a domain, but we are hosting mail and a webserver on > a subdomain. > My understanding is that a name can have more than one associated IP adress > but not the otherway around. Is that within the same domain or accross all > domain names. Correct. A given domain name can have more than one A record, but a given IP address should only have one PTR record (you _can_ have more than one PTR for an address but it's generally Not a Good Idea[tm]). Since DNS records are not returned in any particular order, there's no way to control what domain name a PTR query will yield when there's more than one. In the context of your question, this is true across all domain names. In reality, there's only one domain involved, though, i.e. the in-addr.arpa. domain of the IP address, which is where the PTR record is defined. > IE. As I look at their DNS they have routed the subdomain to our webserver > with an A record www.subdomain.domain.com A xxx.xxx.xxx.xxx > > If you did a resolution of that IP address you'd get our actual name of the > webserver in our own different primary domain. For the most part, that's a good thing. Protocols that do reverse look-ups are usually looking for the 'canonical' name of the machine they're dealing with. > Is this a non-issue, or should I get them to change the A record to a cname? In this case an A and a CNAME are functionally the same -- they're both used to resolve a domain name to an IP address, so it's a non-issue. However, you should make sure that any relevant MX records point to the same name as the machine's PTR (its canonical name): subdomain.domain.com. MX mailserver.your.domain. Christopher Bort

Messages In This Thread: more than one name for an IP address by Systems on May 17, 2000 at 1:18:06 pm Re: more than one name for an IP address by Global Homes Webmaster on May 17, 2000 at 1:50:30 pm Re: more than one name for an IP address by Men & Mice Support on May 17, 2000 at 7:58:54 pm Re: more than one name for an IP address by Jerry Pasker-Systems Admin. on May 30, 2000 at 2:51:04 pm Re: more than one name for an IP address by Men & Mice Support on May 30, 2000 at 3:11:16 pm Re: more than one name for an IP address by Jerry Pasker on May 30, 2000 at 9:13:12 pm