Redirecting web proxy access when the server name changes

Despite the problems I experienced migrating from Proxy Server 2.0 to ISA Server 2004 last night, I did have some success using a little DNS trickery to avoid changing the proxy settings on all clients (the new web proxy server has a different name to the old one). Here’s how it works:

  1. In DNS, delete the original host address (A) record for the old server.
  2. Next, create a host address record for the new server and an alias (CNAME) record with the name of the old server, pointing to the fully qualified domain name of the new server.

All DNS lookups for the old server should be redirected to the new server (via the DNS alias), allowing the proxy settings in the web browser to be updated at leisure (of course, in an Active Directory environment, they could also be updated via group policy).

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