DNS64 Calculator
Size a DNS64 resolver: synthesis rate, cache footprint and the share of queries needing AAAA synthesis.
Inputs
AAAA Records Synthesised
4,200
Cache Memory
84 MiB
Natively Answered Queries
7,800
Share Requiring Synthesis
35.0%
Step by step
Values used
DNS queries per second = 12,000 qps; Destinations that are IPv4-only = 35 %; Distinct names cached = 400,000 entries; Bytes per cache entry = 220 bytes
DNS64
synthesis rate = queries per second × share of IPv4-only destinations; cache memory = cached names × bytes per entry.
AAAA Records Synthesised
= 4,200
Cache Memory
= 88,000,000
Natively Answered Queries
= 7,800
Share Requiring Synthesis
= 35.0
How it works
DNS64 answers AAAA queries for IPv4-only names by synthesising a record inside the NAT64 prefix. Only the IPv4-only share needs synthesis; the rest is answered natively and can be cached normally. DNS64 sits on the critical path of every connection in an IPv6-only network, so undersizing its cache turns a name lookup into the slowest part of the request.
Formula
DNS64
synthesis rate = queries per second × share of IPv4-only destinations; cache memory = cached names × bytes per entry.
- share
- Proportion of destinations with no AAAA record
- entryBytes
- Average size of a cached record set
Frequently Asked Questions
How is DNS64 calculated?
synthesis rate = queries per second × share of IPv4-only destinations; cache memory = cached names × bytes per entry. DNS64 answers AAAA queries for IPv4-only names by synthesising a record inside the NAT64 prefix. Only the IPv4-only share needs synthesis; the rest is answered natively and can be cached normally.
Why does DNS64 matter?
DNS64 sits on the critical path of every connection in an IPv6-only network, so undersizing its cache turns a name lookup into the slowest part of the request.
What values do I need to enter?
This calculator takes 4 inputs: DNS queries per second, Destinations that are IPv4-only, Distinct names cached, Bytes per cache entry. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.