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SIP URI Dialling

Hi All,

I'm trying to setup URI dialing using 3rd party SIP endpoints registered to CUCM v9.x and so far have managed to get it working using ip addresses (extn 1000@ however I can't seem to make it work using a domain name (extn

I believe the problem is to do with setting up a SRV DNS record which I've tried to setup however I can't seem to make it work, does anyone have details of how to set this up using Microsoft DNS server? As haven't been able to find a decent example anywhere.

I'm certainly no expert in DNS or SRV records to please be gentle, however any help or pointers would extremely helpful, I'm also open to ideas if anyone thinks I'm way off track!!

Thanks in advance

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VIP Mentor

SIP URI Dialling

If you want to use DNS or SRV records, then on your DNS server you need to create both alias address record under your domain and reverse lookup..You also need to assign your DNS server to CUCM.

You also need to use a particular host under your eg,,, then create an alias and a reverse lookup record for server1 under the paremt domain:

So your sip trunk destination will be

Hav a look here to see how to configure a reverse lookup record

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SIP URI Dialling

Thanks for your reply, however I don't believe you have understood the question therefore I will try and explain it a little clearer....................

There is NO SIP trunk involved, what I'm after is details on using 3rd party SIP endpoints registered to CUCM and for them to be able to URI dial using the format to another endpoint - This will quite obviously be directed to the DNS server which will need a SRV record to forward the INVITE to the CUCM.

I'm not looking for generic details on how to setup a SRV record, I'm looking for the details on setting up a Microsoft DNS server with a specific SRV record which forwards * to the CUCM.

I'm assuming it the SRV record needs to be something like _sip.udp_ but can't find anything which defines it.

SIP URI Dialling

If the phone is doing a DNS SRV lookup then it isn't registered to CUCM as a SIP Proxy/Registrar. If it was then it should be sending an INVITE with the To header set as '' directly to CUCM.

The DNS SRV record is used by other SIP Proxies (e.g. a gateway or another PBX) which need to lookup what is servicing SIP requests for In this case you create A records for the CUCM nodes, then SRV records which resolve to the A records. For example: 86400 IN SRV 10 0 5060 86400 IN SRV 20 0 5060 86400 IN SRV 10 0 5060 86400 IN SRV 20 0 5060

The important part is that CUCM needs a SIP trunk for this other entitty before it will accept the arriving INVITE. It won't just accept a request from an unknown entitiy; this would be a massive security/toll-fraud hole.

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SIP URI Dialling

Thanks Jonathan,

This makes sense, I will re-register the 3rd party devices as SIP Proxy/Registrar and give it another go................

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