---
title: "IPv6"
description: "5 posts about IPv6, summarised, each linking to the original."
---

# IPv6
> 5 posts about IPv6, summarised, each linking to the original.

## Articles

### [Launching Redis by Upstash](https://yomu.fyi/post/launching-redis-by-upstash.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Dec 15, 2022
- Type: Announcement

Fly.io and Upstash launched a managed Redis service positioned close to Fly.io applications, with global replicas, a free tier, and private encrypted IPv6 connectivity. The integration uses Flycast, Machines API, WireGuard networking, and PROXY protocol headers: flyctl provisions a Flycast IP, routes it through global proxies to the nearest healthy Redis instance, and lets multitenant Redis identify the customer database without exposing its password. Applications can add replicas and write forwarding through flyctl while retaining a single Redis URI; writes go to the primary and reads and writes use geographically nearest replicas. The post illustrates edge HTML caching for a Rails recipe app, reporting low-millisecond global time to first byte for cached GET requests. It also describes read-your-own-write handling, including a 500ms replication wait and fallback reads from the source of truth.


### [Logbook - 2022-05-13](https://yomu.fyi/post/logbook-2022-05-13.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: May 13, 2022
- Type: Announcement

The May 13, 2022 log records Fly.io changes and fixes from the preceding week, spanning infrastructure capacity, account self-service, API maintenance, documentation, and customer-facing behavior. New servers in syd, iad, and dfw, plus three workers in ord, addressed capacity shortages that had caused provisioning or deployment problems. The API moved to Ruby 3.1, with anticipated performance and security-patch benefits, while an internal Elixir UI guide and clearer app and machine name validation errors aimed to reduce development and debugging friction. Operational work permanently disabled consul-templaterb on fly-proxy nodes and fixed a fly-proxy memory leak, giving those nodes more CPU/RAM headroom; an MTU workaround was intended to improve IPv6 tunnel connectivity, while a larger fix remains. Other fixes covered account-deactivation guidance, personalized support email addresses for paid plans, billing, volume metrics, forum registration, and a minor “X daysago” display error.


### [32 Bit Real Estate](https://yomu.fyi/post/32-bit-real-estate.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Oct 18, 2021
- Type: Explainer

Fly.io’s globally distributed network needs routable IPv4 addresses because it assigns distinct public addresses to applications, including non-HTTP services such as UDP DNS servers and TCP game servers. The post explains how address control depends on Regional Internet Registry transfers, a BGP4 ASN, upstream peering, and advertising the same address from multiple locations for Anycast routing. IPv6 and TLS SNI can reduce address demand, but IPv6 connectivity remains unreliable for many users and SNI does not cover non-TLS applications; keeping separate provisioning paths is also considered undesirable. IPv4 blocks are therefore bundled with apps, while outright acquisition is preferred to leasing because addresses can remain assigned indefinitely, despite future IPv6 obsolescence and the risk that their value could eventually fall to zero.


### [IPv6 WireGuard Peering](https://yomu.fyi/post/ipv6-wireguard-peering.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Dec 23, 2020
- Type: Announcement

Fly.io presents WireGuard Peering as a way to connect applications running on its platform privately to AWS, GCP, or other networks, while preserving automatic communication among apps in an organization. Each organization receives a private IPv6 network called a 6PN, with addresses encoding organization, host, and instance identifiers; BPF enforces isolation, and internal DNS resolves app, regional, and peer names. Because WireGuard’s cryptokey routing does not allow overlapping Allowed IPs, Fly swaps the address’s network and host chunks before and after routing, giving the mesh non-overlapping prefixes without changing IPv6 checksums. Users create regional peer configurations with flyctl wireguard create, receiving /120 delegations and organization-specific DNS. The post says this works for database gateways such as an AWS RDS setup, direct app-instance access, and arbitrary services, with connectivity remaining direct between nodes.


### [More Fly Answers To Questions](https://yomu.fyi/post/more-fly-answers-to-questions.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Sep 2, 2020
- Type: Explainer

This Q&A addresses three operational questions about Fly: running non-HTTP applications, identifying connection IP ranges, and renaming applications. Non-HTTP apps need a network service for Fly’s default TCP or optional HTTP health checks; otherwise, Fly may kill them, although Worker process support is planned. For connectivity controls, Fly says AS40509 ranges may not match source addresses seen by servers and advises treating Fly IPs as changeable, while client certificates over TLS offer improved authentication. Future IPv6 per-application addresses could support firewall allowlists. Renaming currently requires creating a new app with flyctl init, claiming the desired name, changing fly.toml, redeploying, and manually restoring secrets, certificates, hostnames, scaling, regions, and other configuration, while sacrificing the original app’s history.