Access URL in CompanyA from CompanyB with Two Way Transitive Trust and DNS

I'm trying to access CompanyAWebsite.CompanyA.com from CompanyB without having to type in the FQDN and vise versa.

I thought this was the purpose of CNAMES in DNS but I must be doing something wrong. Domains have two-way transitive trust currently. Accessing http://CompanyAWebsite.CompanyA.com is successful, but accessing http://CompanyAWebsite is not.

The problem here is that email notifications are being generated to users which are inaccessible unless they manually change the link in the email and add the domain name.

• Add CompanyA.com to the DNS search suffix list for computers in Company B.
• Change the emails to use FQDN, which is a really good idea, regardless.

CompanyAWebsite isn't an FQDN. It's a single label name. It can't be resolved by the CompanyB DNS servers because by default CompanyB DNS clients will append their own DNS suffix to the query and the CompanyB DNS servers will return NXDOMAIN because no such record exists in the CompanyB DNS zone. It can't be forwarded to the CompanyA DNS servers because it's not an FQDN in the CompanyA DNS zone.

The easiest solution is to create a DNS zone in the CompanyB DNS servers named CompanyAWebsite.CompanyA.com and add a "same as parent" A record with the ip address of the website.

As an alternative to the above, you could add CompanyA.com to your DNS suffix search list in CompanyB, but I probably wouldn't go that route myself.