Isolating the carve-out’s traffic and identities from the parent while maintaining secure connectivity during transition is a high-risk, high-complexity task. A phased, standards-driven approach prevents outages, data leaks, and TSA over-runs.
Objectives
- Provide the new entity with an independent, secure, and scalable network and identity stack on Day 1.
- Maintain controlled inter-company connectivity for remaining TSAs.
- Eliminate shared credentials, IP overlap, and monitoring blind spots.
Scope Overview
- Wide-area network (WAN or SD-WAN), internet gateways, VPN concentrators.
- Local networks (LAN / Wi-Fi) at offices, plants, and data centres.
- Cloud VPCs / VNets, load balancers, firewalls, and peering links.
- Identity platforms (Active Directory, Azure AD, Okta) and certificate authorities.
- Monitoring, logging, and intrusion-detection systems.
Step-by-Step Separation Process
- Current-State Discovery
1.1 Map all network segments, IP ranges, routing tables, and firewall rules.
1.2 Catalogue domain forests, trust relationships, and privileged-access groups. - Design Target Network & Identity Architecture
2.1 Allocate new IP address space; reserve overlap buffer for dual-running.
2.2 Define zero-trust segmentation tiers (user, server, OT, DMZ).
2.3 Select independent DNS, DHCP, NTP, and PKI services. - Interim Connectivity Plan
3.1 Establish encrypted site-to-site tunnels or dedicated MPLS links for TSA traffic.
3.2 Enforce strict firewall ACLs and data-loss-prevention policies on inter-company links. - Active Directory & Identity Split
4.1 Create new domain(s); configure conditional access and MFA.
4.2 Migrate user objects, groups, and service accounts using staged cut-over tools.
4.3 Terminate cross-forest trusts immediately after Day 1 validation. - Network Hardware & Cloud Provisioning
5.1 Procure edge routers, firewalls, SD-WAN appliances, and Wi-Fi controllers.
5.2 Build separate cloud subscriptions or accounts; replicate security groups and route tables. - Pilot Cut-Over
6.1 Select a low-risk site; switch routing to the new core; validate latency, packet loss, and identity auth.
6.2 Fix issues and update run-books before rolling out globally. - Global Roll-Out & Day 1 Preparation
7.1 Sequence sites based on business criticality and time zones.
7.2 Execute change windows; update DNS records; monitor health dashboards.
7.3 Freeze shared-network changes 72 hours before legal close. - Post-Cut-Over Hardening
8.1 Remove residual VPN tunnels once TSA services exit.
8.2 Conduct external penetration test and internal segmentation audit.
8.3 Enable full-stack monitoring (NetFlow, IDS/IPS, SIEM) under the new SOC.
Deliverables
- Target-state network topology diagrams and IP plans.
- Identity-migration run-books and rollback procedures.
- Firewall rule-sets and inter-company ACLs with expiry dates.
- Site-by-site cut-over schedule and success-criteria checklist.
- Post-migration penetration-test and segmentation-audit reports.
Common Pitfalls
- Overlooking hard-coded IP addresses in legacy applications, causing post-cut-over failures.
- Retaining open trusts or legacy admin accounts that create security back-doors.
- Under-provisioning bandwidth on interim tunnels, leading to TSA performance issues.
- Failing to align network changes with data-migration freeze windows, resulting in replication errors.
- Neglecting to migrate monitoring and alerting, leaving the new network blind to early threats.
A disciplined network and systems separation—anchored in zero-trust principles and rigorous testing—delivers a secure, performant backbone for the standalone company while allowing controlled collaboration with the parent until all TSAs expire.
