PMN authoritative DNS server
We currently don't have a product to cover this type of service, but our customers normally install two DN servers (usually Berkeley bind but others are possible) and put the RRs there.
These are the servers declared in IR.21 section 17 "List of PMN authoritative DNS server IP addresses and names"
The DNS should be accessible from GRX/IPX and authoritative for two zones:
2G/3G SGSNs without S4 interface form a name like <APN>.mnc001.mcc001.gprs and expect A records of the GTP-C interface(s) of the GGSN/PGW(s)
LTE SGWs and SGSNs with S4 form a name like <APN>.apn.epc.mnc001.mcc001.3gppnetwork.org and use a more complex scheme returning first NAPTR (with preference and order) and then A records.
Example for APN "internet" in zone mnc001.mcc001.gprs:
internet IN A 192.168.196.14 internet IN A 192.168.196.15
Example for APN "internet" in zone mnc001.mcc001.3gppnetwork.org:
internet.apn.epc IN NAPTR 100 10 "a" "x-3gpp-pgw:x-s8-gtp" "" pgw.epc internet.apn.epc IN NAPTR 110 10 "a" "x-3gpp-pgw:x-gp" "" pgw.epc internet.apn.epc IN NAPTR 100 10 "a" "x-3gpp-ggsn:x-gp" "" pgw.epc pgw.epc IN A 192.168.196.14 pgw.epc IN A 192.168.196.15
internet.apn.epc IN A 192.168.196.14 internet.apn.epc IN A 192.168.196.14
The last two records are not mandatory but are provided as a fallback
Various other scenarios are possible with fallback PGWs (via order in NAPTR) or with DNS views (split horizon) directing the session to "nearest" gateway but they probably don't apply to you.