Network & Infrastructure / IPv6, TCP & Transport Engineering
Plan IPv6 subnet boundaries without extending one LAN everywhere
A site stretches one IPv6 subnet across several buildings to avoid changing addresses during moves. The resulting shared neighbor domain increases the impact of loops and discovery faults.
Environment and inputs: Dual-stack routed networks and transport endpoints; validate the complete path and the active operating-system version. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Inventory actual Layer-2 domains, routing boundaries, address requirements and host assumptions. Compare the stretched topology with a routed design that assigns an appropriate subnet to each link.
Explain the result
IPv6 addressing architecture and neighbor discovery operate with link assumptions. Address abundance does not remove failure-domain boundaries or make an arbitrarily large bridged segment operationally desirable.
Plan the fix
Design routed subnet ownership and workload mobility separately, using supported address management and service-discovery mechanisms. Avoid treating a shared address prefix as the only way to retain service identity.
Check the result and rollback
Validate discovery, routing and application naming after a representative move. Revert migration steps if hosts depend on undocumented same-link behavior, and update those dependencies before expanding the rollout.