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DNS repointing after leaving the MWS

How to arrange for your DNS entry to point to another provider outside the University after your site has been migrated off the Managed Web Service (MWS)

Constraints

Control of their DNS is, in general, delegated to individual institutions. Unfortunately, in order to minimise potential issues there are some constraints which mean that the changes need to be coordinated with .

The constraints are:

  1. You can't point a CNAME at a name in a domain to which you don't have access.
    For example, you can't make www.project.botolphs.cam.ac.uk point at server.webprovider.com because you don't have access to webprovider.com

  2. You can't register an address against a name of which you don't have access to the address.
    For example, you can't make www.project.botolphs.cam.ac.uk point at 6.7.8.9 because you don't control the IP address 6.7.8.9.

Over time the IP-register team expects to address these constraints.

Currently available options

Currently, there are two options depending on what you need to do. Your choice will probably depend on how your new service provider wants to operate.

Scenario: one internal host wants to point to one external host using a CNAME address record

UIS prefers the CNAME for a number of reasons.

For a CNAME, you email with the following information:

  1. the internal name, e.g. www.project.botolphs.cam.ac.uk
  2. the external name, e.g. server.webprovider.com
  3. a purpose (required by the database), e.g. Project conference website
  4. when you want the change activated.

Note: Although 'CNAME chaining' (where you have a CNAME pointing at a CNAME) is generally not good practice, it is acceptable here if it is appropriate to have the remote target name a CNAME.

Scenario: for an IP address (not preferred)

Compared to a CNAME, IP addresses are slightly more complex to implement and are not the preferred option because:

  • they will not track changes in the remote host's address (unlike a CNAME, where the address of the target name can move)
  • they also don't handle IPv6 unless explicitly added (Mythic Beasts, for example, heavily promotes and enables IPv6 for all sites).

If you have a number of names, UIS may elect to bulk change them behind the scenes using SQL queries against the database, rather than having to manually update entries.

Please email  with:

  1. the internal name
  2. the external IP address - e.g., 6.7.8.9
  3. when you want the change activated.

Note: The cam.ac.uk DNS updates once per hour, at *:53 minutes past each hour, and requires that the IP Register team manually prepare the change in advance of the next update. For example, if you want the DNS updated at 09:53, UIS would typically make the change about 09:10 and it would go live shortly after 09:53.

Options for hosting multiple cloud-based services

There are some other options which may apply if you are planning on hosting significant number of services in a cloud like fashion. If you need to consider more complicated solutions, the IP Register should be able to assist.

 

First published: 29 March 2021