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Migrating from SD-WAN to SASE: A 90-Day Playbook for IT Infra Managers

December 4, 2025 | 4 mins Read | By Yogita
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SD-WAN to SASE Migration
This 90-day SD-WAN to SASE migration playbook gives IT Infra Managers a practical pathway—from auditing legacy networks to designing identity-first access, PoP selection, routing models, and ZTNA cutover workflows for multi-site enterprises.

Most Indian enterprises deployed SD-WAN for better bandwidth control and cost savings, but in 2025, SD-WAN alone is no longer enough. With remote work, SaaS-heavy environments, and rising cyberattacks, IT Infra Managers are under pressure to modernize their network stack without business disruption.
This 90-day migration playbook offers a practical, execution-ready roadmap—from auditing the current SD-WAN fabric to adopting identity-first access, redesigning routing models, shifting from VPN to ZTNA, selecting the right SASE PoPs, and managing rollout workflows across branches.
If you’re leading a transition from SD-WAN to SASE, this is your blueprint.

1. Audit Phase (Days 1–15)

A successful migration starts with ground truth visibility of the current SD-WAN environment.

1.1 Inventory of existing environment

  • MPLS circuits, broadband links, LTE uplinks

  • Branch firewall models + software versions

  • SD-WAN controllers, CPE devices

  • Current QoS, steering policies

  • VPN concentrators & load distribution

1.2 Traffic flow + dependency mapping

Map:

  • SaaS traffic

  • Cloud workloads

  • Internal apps

  • Guest traffic

  • Branch-to-branch flows

1.3 Security posture analysis

Check:

  • Encrypted traffic inspection gaps

  • SWG/CASB coverage gaps

  • Lateral movement exposure

  • Lack of identity-based segmentation

1.4 Identify choke points

Typical SD-WAN bottlenecks:

  • Backhauling to data center for security

  • Inconsistent branch policies

  • High latency for Office 365, Salesforce, SAP, etc.

Also Read: SASE Architecture Blueprint for Indian Enterprises (2025)

2. Identity-First Approach (Days 15–30)

Migrating to SASE requires identity > network.

2.1 Move away from IP-based controls

SD-WAN policies often rely on:

  • Source IP

  • Subnet tagging

  • VLAN segmentation

SASE shifts control to:

  • User identity

  • Device posture

  • Risk score

  • Least privilege access

2.2 Integrate IAM + IdP

Before rollout, integrate:

  • Azure AD / Google Workspace / Okta

  • MFA

  • Conditional access

  • Device compliance policies

2.3 Define identity-based segmentation

Segment:

  • Contractors

  • Developers

  • Finance

  • OT/ICS devices

  • Partners

This becomes the backbone of ZTNA and app-level controls.

3. Branch Routing Model (Days 30–45)

This is where SD-WAN meets SASE.

3.1 Choose routing strategy

Three primary models:

Model A — Direct-to-PoP (Recommended)

Traffic from branches goes to nearest SASE PoP for:

  • Security inspection

  • Policy enforcement

  • Cloud breakout

Best for:
SaaS-heavy and multi-site enterprises.

Model B — Hybrid PoP + DC

Critical internal apps route to DC.
Everything else routes to PoPs.

Best for:
Enterprises with large on-prem workloads.

Model C — Phased per-site migration

Move low-risk branches first, critical sites later.

Best for:
Large distributed networks with >20 branches.

3.2 Define SLAs for branch cutover

  • PoP latency (must be <20ms ideally)

  • Failover route plans

  • CPE firmware alignment

  • Traffic steering logic

Also Read: SASE Architecture for Multi-Site Enterprises

4. VPN to ZTNA Cutover Plan (Days 45–60)

You can’t migrate to SASE without replacing VPN for users first.

4.1 Hybrid mode (VPN + ZTNA)

Run both temporarily; gradually shrink VPN usage.

4.2 App-by-app ZTNA migration

Start with:

  • Internal web apps

  • SaaS management portals

  • Dev servers

  • Partner portals

Then move to:

  • Critical business apps

  • HRMS / ERP / Finance

  • OT systems (if applicable)

4.3 User groups cutover plan

  1. IT + power users

  2. Developers

  3. Corporate staff

  4. Field teams

  5. Contractors/vendors

4.4 Decommission VPN concentrators

Only when:

  • All apps migrated

  • All users shifted

  • Monitoring baseline established

  • Policy tuning completed

Outcome:
Your risk window from lateral movement shrinks dramatically.

Also Read: SASE vs VPN 2025

5. SASE PoP Planning (Days 60–75)

PoP selection directly impacts performance.

5.1 Verify PoP presence near your branches

Critical PoPs for Indian enterprises:

  • Mumbai

  • Chennai

  • Hyderabad

  • Bengaluru

  • Delhi NCR

5.2 Validate throughput + SLAs

Ask vendors for:

  • PoP latency benchmarks

  • Packet loss reports

  • Private backbone routes

  • Peak hour performance data

5.3 Evaluate backbone advantage

Vendors using private backbones (like Cato, Aryaka) deliver:

  • Lower jitter

  • Predictable throughput

  • Shorter SaaS round-trip time

5.4 Redundancy planning

  • Dual PoP connections

  • Failover routing logic

  • Automatic RTO policies

Also Read: FWaaS Providers Compared

6. Rollout Workflows (Days 75–90)

A predictable execution plan ensures zero business disruption.

6.1 Branch rollout sequence

  1. Low-traffic branches

  2. Medium branches

  3. High-traffic hubs

  4. Data center

6.2 Communication templates

Prepare:

  • User training guides

  • App access changes

  • Expected downtime window

  • Quick troubleshooting workflows

6.3 Validate security + performance KPIs

  • ZTNA login latency

  • PoP RTT

  • Branch traffic distribution

  • SLA adherence

  • Policy enforcement accuracy

6.4 Shift to BAU Mode

Hand over final configuration to:

  • SOC

  • Network team

  • IT Ops

  • Compliance teams

Outcome of the 90-Day Playbook

  • Centralized SASE policies

  • App-level access

  • Lower latency for SaaS

  • Reduced VPN dependencies

  • Better threat visibility

  • Stronger compliance posture

TAGS

Cato Networks
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