Two stages for the same estate. First an ISP cutover and enterprise migration carrying a full public IP renumbering — routing, GRE tunnels, VPN, NAT and DNS reconfigured through to production cutover and service validation. Then WAN and remote connectivity modernization, with CRM, messaging and hosted application connectivity maintained across it.
Renumbering an estate’s public address space is one of those changes where the plan either accounts for everything that hard-codes an address, or it does not, and you find out at cutover. The addresses are rarely all in the places anyone documented: they turn up in firewall rules, in a partner’s allowlist, in a certificate, in an application config nobody has opened in six years. The work is the inventory, not the reconfiguration.
Outcome
A cutover where the address change was found in the plan rather than at the switchover.