IAD132E connect to IMS via sip trunk. but it failed to query the domain name of IMS. the DNS request failed.
but other vendor's product works well.
Login to the web page of IAD. select "SIP Service Configuration > SIP Server > SIP Server Obtain type" as "STATIC". and then test again, problem solved.
Make a network captures of both IAD & the normal DNS request. Compare result as below snip. the only difference is : TYPE of the DNS request from IAD is SRV, but from the normal DNS request is A.
then we check the configuration by command "disaply current configuration" and found this line:
so the problem is clear --- customer make wrong configuration of the dns mode.
We should be more carefully with the configuration. before change them, we must get clear what it means.