chore(docs): initial compit of the IPv6 docu

infrastructure/ipv6.md

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+# IPv6 – Overview and Best Practices
+
+## Why IPv6?
+IPv6 was introduced to address the limitations of IPv4, most notably the shortage of available addresses. It provides an almost unlimited address space, improved support for modern networking, and forms the foundation for future-proof infrastructures.
+
+## DNS instead of IP addresses
+- IPv6 addresses are long and difficult to memorize (e.g. `2001:db8:85a3::8a2e:370:7334`).  
+- It is therefore recommended to use **DNS names for virtual machines (VMs)** and other systems.  
+  → This improves administration, readability, and reduces error potential.
+
+## Own IPv6 Stack
+- The **RFC4193 range** (`fd00::/8`) is reserved for **local, private use**, similar to private IPv4 networks (e.g. `192.168.x.x`).  
+- For production environments, it is preferable to use **public, globally routable IPv6 prefixes** obtained from an ISP or an own IPv6 allocation.  
+  → Advantages:  
+  - Unique addressing without overlaps  
+  - Direct reachability and routability on the Internet  
+  - Sustainable, future-oriented network design
+
+## Dual Stack as a Transition Strategy
+- In many environments, IPv4 cannot be replaced immediately.  
+- **Dual Stack** allows IPv4 and IPv6 to operate in parallel.  
+- This enables a gradual transition to IPv6 without requiring a complete redesign of the network infrastructure at once.  
+- Dual Stack can be maintained as long as necessary, until IPv6 adoption is complete.
+
+## Jump Host for IPv6-only Zones
+- When migrating to **IPv6-only environments**, not all clients or tools may yet support IPv6.  
+- A **Jump Host** with both IPv4 and IPv6 connectivity can serve as an entry point.  
+- It enables access from IPv4-based networks into IPv6-only segments, acting as a controlled and secure bridge during the transition phase.  
+- This approach ensures operability while gradually phasing out IPv4.
+
+## Conclusion
+IPv6 is essential for modern IT infrastructures and significantly simplifies network management in the long term.  
+By relying on **DNS names instead of raw IP addresses**, operating an **own, globally valid IPv6 stack**, using **Dual Stack during the migration phase**, and providing a **Jump Host for IPv6-only zones**, networks become more robust, scalable, and future-proof.