Can CNAMEs be used to point to Name Servers

DNS data is cached in servers around the world. Checking your servers for changes is likely to mislead you as to whether a change has been made or not.

Looking at your data from here shows that your changes have been made. It looks like your TTL (Time To Live) is about four hours so your changes should be visible to you as well.

When making major changes it is best to make changes in a manner that uses the old and new addresses for a transitional period. One approach would be to publish both the old and new ip addresses at least on TTL period. Then when the transition occurs DNS will have the new addresses to use. Once the transition is done the old IP addresses can be removed.

It is common to change the TTL to a low value prior to the change so that cached data will be refreshed quickly. Scaling down the TTL over a period of time can be used limit the period when most requests are handled by your listed name servers.

EDIT: You can check what various name servers have in their cache with the nslookup or host (newer Linux/Unix distributions) command. You could try google (8.8.4.4 or 8.8.8.8) or OpenDNS (208.67.220.220 or 208.67.222.222) to see what some major caches have. The command for one of the name servers listed above is:

nslookup  ns1.vertigo.bm 8.8.8.8

The timetable I use for scaling down TTL is to reduce it by half whenever the time until the change is twice the current TTL. Keep the TTL at least five or ten minutes. Add the new addresses to the active nameservers 10 to 20 minutes in advance of the change. Remove the old entries after the change has been accomplished.

So you are not looking at redirection as such (as that happens at the app level, i.e. on Apache/Nginx/wherever) but rather on the DNS resolution. The host on which DomainA is hosted will or should never be hit, based on your description as you want the DNS requests to be resolved to the IPs of DomainB. Unless I'm missing something in your request?

As Shane pointed out DNS is not capable of HTTP redirection - that's an application/webserver duty. You could make DomainA and DomainB resolve to the same IP on DNS and all would work. But if you're looking to do this on per URL/per-path way then this is not possible - DNS is not capable of that - it's a simple DNS->IP service, what's happening with the actual URL is the webserver's task.

After the comment below, what I'd do is to refer all DNS records for DomainA to the same IP(s) as DomainB is pointed to - this way you will get HTTP request hitting hostB and then it's just a simple matter of:

1. creating a particular Apache Name Baseed Virtual host - which will be serving files from its own DocumentRoot
2. creating permanent redirect on Apache like this:

This will rewrite anything coming to DomainB to DomainA which can be hosted on the same server or somewhere else. I appreciate that the second option is probably an overhead and not necessary if you can/are allowed to create Name Based Virtual hosts on apache.

<VirtualHost *:80>
  ServerName DomainB
  Redirect permanent / http://DomainA/
</VirtualHost>

I'd go with 1. - point all DNS records of DomainA to the same IP(s) as DomainB is pointing and create particular Name Based VirtualHosts on Apache.