IPv6-Only Networks: Is the Future Here?
Explore IPv6-only network deployments, how 464XLAT and NAT64 enable IPv4 compatibility, and which organizations have already made the switch.
The Case for IPv6-Only
Dual-stack (running IPv4 and IPv6 simultaneously) was always meant to be transitional. An IPv6-only network eliminates the complexity and cost of maintaining two protocol stacks:
- Simpler operations -- One set of firewall rules, one routing protocol instance, one addressing scheme.
- Lower costs -- No IPv4 address purchases ($30-50+ per address).
- Reduced attack surface -- Only one protocol to secure.
- Better performance -- No dual-stack latency overhead.
Who Is Already IPv6-Only?
Several major organizations run IPv6-only networks in production:
| Organization | Network | Since | Scale |
|---|---|---|---|
| T-Mobile US | Mobile network | 2014 | 100M+ devices |
| Reliance Jio | Mobile network | 2016 | 400M+ subscribers |
| Apple | Corporate Wi-Fi + data centers | 2018 | Internal |
| Facebook/Meta | Data center fabric | 2017 | Millions of servers |
| Microsoft Azure | Internal backbone | 2019 | Cloud-scale |
| SKT (South Korea) | Mobile 5G | 2020 | 30M+ subscribers |
These networks use NAT64/DNS64 or 464XLAT for backward compatibility with IPv4-only destinations.
How IPv4 Compatibility Works
NAT64 + DNS64
For most traffic (web, APIs, email), NAT64 + DNS64 transparently handles IPv4-only destinations:
App requests: example-v4only.com
DNS64 returns: 64:ff9b::93.184.216.34 (synthesized AAAA)
Device connects: IPv6 to NAT64 gateway
NAT64 translates: IPv6 -> IPv4 -> destination
The application never knows it is on an IPv6-only network.
464XLAT for Legacy Apps
Some applications use literal IPv4 addresses or IPv4-only APIs. 464XLAT (RFC 6877) solves this with a client-side translator:
Legacy app (IPv4) -> CLAT (device-local NAT46) -> IPv6 network -> PLAT (NAT64) -> IPv4 internet
The CLAT provides a local IPv4 address (typically from 192.0.0.0/29) that legacy apps can bind to. Android, iOS, and Windows all include CLAT support.
Challenges of IPv6-Only
Literal IPv4 Addresses
Applications that hardcode IPv4 addresses (e.g., http://1.2.3.4/api/) bypass DNS64 and fail. This is the biggest barrier to IPv6-only deployment.
Solution: 464XLAT or application remediation.
IPv4-Only APIs and Services
Some third-party services still lack IPv6 support. Your NAT64 gateway handles this transparently, but you need to monitor for edge cases.
Monitoring and Troubleshooting
Network tools like traceroute, packet captures, and flow analysis need to be IPv6-aware. Staff training is essential.
Getting Started
A phased approach for enterprises:
- Start with new greenfield networks -- new offices, cloud VPCs, IoT segments.
- Deploy NAT64/DNS64 infrastructure at the network edge.
- Test 464XLAT on pilot devices.
- Migrate segment by segment, monitoring for breakage.
- Decommission IPv4 on migrated segments.
The mobile carriers have proven that IPv6-only works at massive scale. The technology is mature -- the remaining barriers are organizational, not technical.