What is dnsmgr_lookup?

When I typed module reload on my asterisk v1.4.18 on its CLI, I noticed my asterisk tried to perform a dns lookup to “” as shown below:

== Parsing '/etc/asterisk/iax.conf': Found == Parsing '/etc/asterisk/users.conf': Found > doing dnsmgr_lookup for '' <========= Where did this come from? == Loaded firmware 'iaxy.bin' == Parsing '/etc/asterisk/iaxprov.conf': Found -- Loaded provisioning template 'default' -- Reloading module 'codec_ulaw.so' (mu-Law Coder/Decoder)
AFAIC, I have never configured my asterisk with a DNS of ‘’. The question is how can I change this ‘’ to other DNS server. Anyone?