Why architecture matters here

IPv6 fails on wrong address plan, half-configured dual stack, and firewall gaps. Architecture matters because dual stack + SLAAC + NAT64 must compose for coexistence.

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The architecture: every piece explained

The top strip is basics. Address plan /48 sites + /64 subnets. Dual stack. SLAAC autoconfig. Neighbor discovery ARP replacement.

The middle row is variants. DHCPv6 when stateful. Link-local fe80::. NAT64 / DNS64 bridge. MTU + PMTUD no fragmentation.

The lower rows are ops. Security IPsec + RA guard. Firewalling. Ops — connectivity + monitoring + migration.

IPv6 — address plan + dual stack + SLAAC + ND + NAT64/DNS64the addressing that IPv4 exhaustedAddress plan/48 sites + /64 subnetsDual stackv4 + v6SLAACstateless autoconfigNeighbor discoveryreplaces ARPDHCPv6stateful when neededLink-localfe80::/10NAT64 / DNS64v6 → v4 gatewayMTU + PMTUDno fragmentationSecurityIPsec native + RA guardFirewallingdifferent rulesOps — connectivity tests + monitoring + migrationconfiglocalbridgediscoverhardenadaptadaptoperateoperate
IPv6 substrate with dual stack, SLAAC, NAT64.
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End-to-end flow

End-to-end: dual-stack host boots. SLAAC assigns v6 address from RA. IPv4 obtained via DHCPv4. Application prefers v6 via Happy Eyeballs. NAT64/DNS64 lets v6-only apps reach v4 legacy. Firewalls updated with v6 rules.