Home > How-tos, Microsoft > Setting up DNS SRV records for an Office 365 migration (on 123-reg)

Setting up DNS SRV records for an Office 365 migration (on 123-reg)

I needed to setup some DNS records for an Office 365 migration earlier and was initially slightly confused translating the settings Microsoft supplied us to those needed as input on 123-reg’s Advanced DNS configuration. The MX, TXT and CNAME records were simple enough, but it was the SRV records that needed a bit of fiddling to get right.

As an example on the SRV records, MS give you something like this:

Type Service Protocol Port Weight Priority TTL Name Target
SRV _sip _tls 443 1 100 1 Hour thedomain.co.uk sipdir.online.lync.com
SRV _sipfederationtls _tcp 5061 1 100 1 Hour thedomain.co.uk sipfed.online.lync.com

123-reg give you this interface to enter SRV records yourself:

Screen Shot 2013-06-13 at 14.24.42


By looking at the examples you can start to understand how to translate the Service, Protocol, and Weight items that MS give you, into the 123-reg input boxes (which do not exist individually for Service, Protocol and Weight).

In the first SRV record example –

Hostname therefore becomes: _sip._tls (the Service + the Protocol with a dot (.) between)

TTL of course becomes: 3600 (1 hr)

Priority is 100

Destination (the most confusing one) becomes: 1 443 sipdir.online.lync.com. (note that it starts with Weight (1), then a space, then the port number (443), then the Target (sipdir.online.lync.com), followed by a dot (.)

That forms your complete SRV record. By entering these along with the other records you require, you should have a fully functional Office 365 setup on your custom domain name.

Categories: How-tos, Microsoft Tags: , , , , , ,
  1. December 30th, 2013 at 10:57 | #1

    Thanks for this. It really helped me. I was scratching my head trying to figure out how to configure the SIP DNS entries on 123-reg.

  2. January 11th, 2014 at 10:33 | #2

    I’ve always had problems with DNS with 123 reg on how their system works. But this makes it very simple and easy to understand. Thank you Sean.

  3. Stephen
    March 22nd, 2014 at 14:17 | #3

    Great stuff.. just the info I needed. I was almost there, but didn’t get where the protocol should have been entered. Many thanks.

  4. Daniel
    April 2nd, 2014 at 12:00 | #4

    Thanks very much – just what I was after!

  5. Nirmal
    August 14th, 2014 at 16:17 | #5

    Sean – very useful.. and simplifies the task. thanks for that. Just one correction in your write up above:
    You say ‘Priority of course becomes: 3600 (1 hr)’ — this should be:
    TTL of course becomes: 3600 (1 hr)
    Priority is 100

  6. August 14th, 2014 at 16:23 | #6

    Hi Nirmal,

    Thanks for the feedback – I’ve fixed that mistake too – cheers!


  7. DJS
    August 30th, 2014 at 00:06 | #7

    Thanks for this. I was struggling to figure out hostname.

  8. Phil
    September 24th, 2014 at 09:16 | #8

    Sean – I’ve had issues with lync when it comes to invites (couldnt accept my own invite from an email but could from the desktop app!).

    Having made the change to “_sip._tls” and “_sipfederationtls._tcp” as well as 3600 (rather than 1) its all working perfectly.

    Been bugging me for a while so I’m very grateful for your clear explanation 🙂

  9. September 24th, 2014 at 09:33 | #9

    Great, glad to hear Phil!

  10. Steve
    January 2nd, 2015 at 21:20 | #10

    A very useful post, helped me sort out Lync set up for a client. Thanks

  11. January 6th, 2015 at 10:35 | #11

    Many thanks for the guide – saved me a load of time setting up Office 365 with a custom domain!

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