Expressway SIP Outbound DNS requests

[fedor.solovev]

Hello, Dear Support Community.

It is jabber, CUCM 10.x, Exp-C/E 8.5.

Each time I dial to external system via SIP URI like 5000@meeting.domain.com, a call is searched in DNS zone.

Exp-E requires NAPTR and then SRV for that domain. Only A-record exists for meeting.domain.com server.

How to configure Exp-E to call outside to SIP URI not sending DRV requests ?
It is necessary if nothing except A-records for external systems in external domains is configured.

[Dennis Mink]

your VCS-e will need to be configured with an external DNS server to resolve non-company DNS names

[fedor.solovev]

Hi,
yes you are right. And it really does.
My point is how to call outside Exp-E to SIP URI only without any SRV requests ?

[PJMack]

You can't - it needs lookup the SIP SRV records to resolve the URI. Read this article, this guy explains how it works pretty well: https://anders.com/cms/263/Tutorial/SIP/DNS/SRV/djbdns

[Patrick Sparkman · Accepted solution]

Expressway will always do DNS lookups, no way to disable it and it is required for video conferencing to work to locate where to send the call to the remote endpoint.
For example, if the called party has an SRV record in their DNS, than it will return the IP/port of their Expressway where the remote endpoint can be reached at. If no SRV record is found (or no SRV search is performed), than the call will fail as there will be no way of locating the remote endpoint's Expressway.