The previous RHEL approach poked kernel sysctls and `ip -6` commands
with wait/retry loops, which was guesswork: convergence depended on RA
timing, DAD completion and the kernel picking the right source address,
and it kept failing intermittently in e2e testing.
RHEL's network stack is NetworkManager, so the deterministic /128 and
the bridge gateway are now declared as a STATIC connection profile:
nmcli con mod <eth0> ipv6.method manual \
ipv6.addresses <det-addr>/128 ipv6.gateway fe80::1
ipv6.method=manual makes NM own the whole IPv6 stack: it sets
accept_ra=0 itself (no kernel RA interference, no SLAAC/dynamic
addresses outside the routed /112), applies the address and default
route atomically, and re-applies the profile on every boot. No daemons,
no waiting, no retries — the profile IS the final state. The
vpsmgr-ipv6 helper unit and the baked sysctl/helper/service are removed
from the image entirely.
Verified: reinstall to Alma 9 and fresh Debian->RHEL reinstall both
converge immediately (ipv6.method manual, accept_ra 0, single /128, no
dynamic addresses, egress + interop OK, stable over time).
Co-authored-by: CommandCodeBot <noreply@commandcode.ai>
