i am on a shared host but i don’t think it could be that
First, do you have access to the hosting service in such a way that you can map the VirtualHost of the blog.clientdomain.com to your webserver?
If not, then you’re screwed and no amount of WordPress trickery will do the job.
Webservers work like this (greatly simplified):
- A browser tries to go to a site.
- The DNS points it to an IP for that site.
- The browser sends a http request to that site saying “give me this site”.
- The webserver looks in its config files, finds the entry for that site (domain name, path, etc) and sees that to serve that site it needs to look in /some/file/path/on/the/server.
The VirtualHost points a URL/path to a directory, more or less. It’s a bit more complex than that but not much. The short of it is that you need your webserver, outside of WordPress itself, to know that it needs to direct requests for this site to your WordPress install.
If you can’t do that, then you just can’t do it at all.
Once you have that working, but don’t have the domain setup yet, then the webserver will direct those requests to your WordPress install. But since WordPress doesn’t know about that domain, it’ll just redirect you to the main site instead, because that is sort of the default fallback position.
Basically, if you have the DNS working, then you don’t get your main blog, then you need to setup the VirtualHost to point that domain to your existing install. Once that works, once it’s loading your page and not some 404, only then can you do Multisite Domain Mapping. Then the standard domain mapping tutorials will work.
How do you do the VirtualHost? On shared, you might not be able to. Ask your host.