Our IMS clients will use DNS service to resolve which transport protocol to preferr and which server provides that SIP service. Therefore we need for this purpose working DNS server with valid delegated zones. In our case we are administrating own DNS zone named ims1.sip.uniza.sk. So we will add required resource records, first we add NAPTR records and then valid SRV and A records
So, prepare your DNS records, in our case:
$ORIGIN ims1.sip.uniza.sk.
@ NAPTR 30 100 "S" "SIP+D2U" "" _sip._udp.pcscf.ims1.sip.uniza.sk.
@ NAPTR 20 100 "S" "SIP+D2T" "" _sip._tcp.pcscf.ims1.sip.uniza.sk.
@ NAPTR 10 100 "S" "SIP+D2T" "" _sip._tcp.pcscf.ims1.sip.uniza.sk.
pcscf IN A 158.193.139.40
_sip.pcscf IN SRV 0 0 5060 pcscf
_sip._udp.pcscf IN SRV 0 0 5060 pcscf
_sip._tcp.pcscf IN SRV 0 0 5060 pcscf
_sips._tcp.pcscfIN SRV 0 0 5060 pcscf
icscf IN A 158.193.139.41
_sip IN SRV 0 0 5060 icscf
_sip._udp IN SRV 0 0 5060 icscf
_sip._tcp IN SRV 0 0 5060 icscf
scscf IN A 158.193.139.42
_sip.scscf IN SRV 0 0 5060 scscf
_sip._udp.scscf IN SRV 0 0 5060 scscf
_sip._tcp.scscf IN SRV 0 0 5060 scscf
hss IN A 158.193.139.43
presence IN A 158.193.139.37