{"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"answer":{"id":"fe2288ec-918d-44a7-bcee-53495ec9fa1c","slug":"how-do-you-migrate-from-on-premises-pbx-to-ucaas","question":"How do you migrate from on-premises PBX to UCaaS?","answerMarkdown":"Migration runs in six phases: audit the existing carrier contract and PBX inventory, validate the network for VoIP, select a UCaaS provider, port numbers, run a parallel pilot, then schedule the production cutover [1][2]. End-to-end timelines run **6 to 16 weeks** for mid-market deployments [3]. The single highest-risk step is number porting — most projects schedule it as the final cutover task with the legacy PBX still live as fallback [4].","answerText":"Migration runs in six phases: audit the existing carrier contract and PBX inventory, validate the network for VoIP, select a UCaaS provider, port numbers, run a parallel pilot, then schedule the production cutover [1][2]. End-to-end timelines run 6 to 16 weeks for mid-market deployments [3]. The single highest-risk step is number porting — most projects schedule it as the final cutover task with the legacy PBX still live as fallback [4]. How to Review the legacy carrier contract Get the contract end date, auto-renewal window (often 30–90 days out), and early-termination fees from your current carrier before doing anything else. Knowing this opens negotiation room with the new provider. Inventory phones, lines, and use cases Document every active phone number per location, distinguish voice from fax/elevator/alarm lines, and capture user preferences: desk phone, softphone, or mobile-only. This sizes the license and hardware order accurately. Validate the network Confirm bandwidth (30 Kbps per concurrent call), turn on QoS to prioritize voice, upgrade switches to PoE if you'll deploy desk phones, and verify the firewall passes SIP traffic without ALG mangling. Select the UCaaS provider and design call flows Match the shortlist against required features (call recording, AI, integrations, compliance). Map every IVR menu, hunt group, and auto-attendant from the legacy PBX into the new platform's admin portal. Submit port orders and run a parallel pilot Open Letters of Authorization to port numbers — porting takes 2 to 6 weeks per carrier. While porting clears, run 10–20 pilot users on the new platform alongside the legacy PBX to surface issues. Cutover and decommission Schedule the production cutover for an off-hours window, validate inbound and outbound calls from every site, keep the legacy PBX powered for 7–14 days as fallback, then decommission hardware and cancel carrier services. Tools and prerequisites Current PBX configuration export Source of call flows, extensions, and number assignments to recreate in UCaaS Carrier contract and CSR (Customer Service Record) Required to validate ownership and submit port orders Network assessment tool Measures bandwidth, jitter, and packet loss before cutover PoE-capable switches Power IP desk phones over the data cable without separate adapters UCaaS admin portal Where you build users, call routing, and auto-attendants in the new platform Project plan and runbook Tracks port dates, pilot users, cutover steps, and rollback triggers Common mistakes Missing the auto-renewal window and getting locked in another year Skipping the network assessment and discovering jitter after cutover Porting numbers before the new platform is tested end-to-end Cutting over during business hours instead of an off-hours window Decommissioning the legacy PBX before a stability soak period Underestimating user training and adoption change-management work Key terms Number porting Workstream Process of transferring existing phone numbers from the legacy carrier to the new UCaaS provider while keeping numbers live. Parallel pilot Workstream Test phase where a subset of users run on UCaaS while the on-prem PBX still handles production traffic. Quality of Service (QoS) Technical dependency Network configuration that prioritizes voice packets over other traffic to keep calls clean during congestion. Power over Ethernet (PoE) Technical dependency Switch capability that powers IP desk phones over the same cable that carries data. Cutover Workstream Scheduled event when production traffic moves from the legacy PBX to UCaaS, usually outside business hours. Related questions How does UCaaS compare to on-premises PBX? /search?q=How+does+UCaaS+compare+to+on-premises+PBX%3F How do you set up UCaaS for a remote team? /search?q=How+do+you+set+up+UCaaS+for+a+remote+team%3F What UCaaS bandwidth requirements should businesses plan for? /search?q=What+UCaaS+bandwidth+requirements+should+businesses+plan+for%3F","answerHtml":"<p>Migration runs in six phases: audit the existing carrier contract and PBX inventory, validate the network for VoIP, select a UCaaS provider, port numbers, run a parallel pilot, then schedule the production cutover <a href=\"https://sangoma.com/blog/how-to-switch-from-on-premises-pbx\" class=\"citation-ref\" data-citation-index=\"1\" target=\"_blank\" rel=\"noreferrer\">[1]</a><a href=\"https://www.continuant.com/blog/the-ultimate-guide-for-migrating-from-legacy-pbx-to-ucaas\" class=\"citation-ref\" data-citation-index=\"2\" target=\"_blank\" rel=\"noreferrer\">[2]</a>. End-to-end timelines run <strong>6 to 16 weeks</strong> for mid-market deployments <a href=\"https://tcinow.com/on-premise-to-cloud-voip-migration-guide\" class=\"citation-ref\" data-citation-index=\"3\" target=\"_blank\" rel=\"noreferrer\">[3]</a>. The single highest-risk step is number porting — most projects schedule it as the final cutover task with the legacy PBX still live as fallback <a href=\"https://www.techmode.com/on-prem-pbx-to-cloud-where-ucaas-and-ccaas-fit-in\" class=\"citation-ref\" data-citation-index=\"4\" target=\"_blank\" rel=\"noreferrer\">[4]</a>.</p>\n","summary":"Migration runs in six phases: audit the existing carrier contract and PBX inventory, validate the network for VoIP, select a UCaaS provider, port numbers, run a parallel pilot, then schedule the production cutover [1][2]. End-to-end timelines run 6 to 16 weeks for mid-market depl","publishedAt":"2026-06-08T19:57:25.984","verifiedAt":null,"editorialStatus":"APPROVED","lastReviewedAt":null,"nextReviewDueAt":null,"templateVersion":"v2","aliases":[],"confidenceScore":null,"confidenceLabel":null,"canonicalUrl":"https://sangoma.com/blog/how-to-switch-from-on-premises-pbx"},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"contributorOrganizationProfile":{"entityId":"ec39deab-44fe-48d8-9029-fefe993ab85a","legalName":null,"description":null,"websiteUrl":null,"imageUrl":null,"slogan":null,"subtitle":null,"facts":[],"coiNote":null,"foundingDate":null,"numberOfEmployeesText":null,"contactPoint":null,"address":null,"headquartersText":null,"organizationType":null},"contributorPerson":null,"sections":[{"id":"f9269311-f394-4238-94cc-9c19c4957591","sectionKey":"methodology","sectionType":"column_section","heading":"How to","introMarkdown":null,"introHtml":null,"outroMarkdown":null,"outroHtml":null,"contentJson":{"columns":[{"heading":"Review the legacy carrier contract","bodyMarkdown":"Get the contract end date, auto-renewal window (often 30–90 days out), and early-termination fees from your current carrier before doing anything else. Knowing this opens negotiation room with the new provider."},{"heading":"Inventory phones, lines, and use cases","bodyMarkdown":"Document every active phone number per location, distinguish voice from fax/elevator/alarm lines, and capture user preferences: desk phone, softphone, or mobile-only. This sizes the license and hardware order accurately."},{"heading":"Validate the network","bodyMarkdown":"Confirm bandwidth (~30 Kbps per concurrent call), turn on QoS to prioritize voice, upgrade switches to PoE if you'll deploy desk phones, and verify the firewall passes SIP traffic without ALG mangling."},{"heading":"Select the UCaaS provider and design call flows","bodyMarkdown":"Match the shortlist against required features (call recording, AI, integrations, compliance). Map every IVR menu, hunt group, and auto-attendant from the legacy PBX into the new platform's admin portal."},{"heading":"Submit port orders and run a parallel pilot","bodyMarkdown":"Open Letters of Authorization to port numbers — porting takes 2 to 6 weeks per carrier. While porting clears, run 10–20 pilot users on the new platform alongside the legacy PBX to surface issues."},{"heading":"Cutover and decommission","bodyMarkdown":"Schedule the production cutover for an off-hours window, validate inbound and outbound calls from every site, keep the legacy PBX powered for 7–14 days as fallback, then decommission hardware and cancel carrier services."}]},"configJson":{"columns":3},"noteMarkdown":null,"noteHtml":null,"sortOrder":0},{"id":"7d5e53d8-719a-4218-a7d7-63bf9e98be6f","sectionKey":"tools_and_prerequisites","sectionType":"cards_section","heading":"Tools and prerequisites","introMarkdown":null,"introHtml":null,"outroMarkdown":null,"outroHtml":null,"contentJson":{"cards":[{"title":"Current PBX configuration export","bodyMarkdown":"Source of call flows, extensions, and number assignments to recreate in UCaaS"},{"title":"Carrier contract and CSR (Customer Service Record)","bodyMarkdown":"Required to validate ownership and submit port 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cutover","bodyMarkdown":""},{"title":"Porting numbers before the new platform is tested end-to-end","bodyMarkdown":""},{"title":"Cutting over during business hours instead of an off-hours window","bodyMarkdown":""},{"title":"Decommissioning the legacy PBX before a stability soak period","bodyMarkdown":""},{"title":"Underestimating user training and adoption change-management work","bodyMarkdown":""}]},"configJson":{"colSize":2,"columns":2},"noteMarkdown":null,"noteHtml":null,"sortOrder":2},{"id":"4cd555af-59b6-496f-a0ad-dfaf06fd33d5","sectionKey":"key_terms","sectionType":"cards_section","heading":"Key terms","introMarkdown":null,"introHtml":null,"outroMarkdown":null,"outroHtml":null,"contentJson":{"cards":[{"title":"Number porting","category":"Workstream","bodyMarkdown":"Process of transferring existing phone numbers from the legacy carrier to the new UCaaS provider while keeping numbers live."},{"title":"Parallel pilot","category":"Workstream","bodyMarkdown":"Test phase where a subset of users run on UCaaS while the on-prem PBX still handles production traffic."},{"title":"Quality of Service (QoS)","category":"Technical dependency","bodyMarkdown":"Network configuration that prioritizes voice packets over other traffic to keep calls clean during congestion."},{"title":"Power over Ethernet (PoE)","category":"Technical dependency","bodyMarkdown":"Switch capability that powers IP desk phones over the same cable that carries data."},{"title":"Cutover","category":"Workstream","bodyMarkdown":"Scheduled event when production traffic moves from the legacy PBX to UCaaS, usually outside business hours."}]},"configJson":{"colSize":3,"columns":3},"noteMarkdown":null,"noteHtml":null,"sortOrder":3},{"id":"a1ab4fc0-deea-47f6-b99d-3873ddb1c79a","sectionKey":"related_questions","sectionType":"cards_section","heading":"Related questions","introMarkdown":null,"introHtml":null,"outroMarkdown":null,"outroHtml":null,"contentJson":{"cards":[{"url":"/search?q=How+does+UCaaS+compare+to+on-premises+PBX%3F","title":"How does UCaaS compare to on-premises PBX?","bodyMarkdown":""},{"url":"/search?q=How+do+you+set+up+UCaaS+for+a+remote+team%3F","title":"How do you set up UCaaS for a remote team?","bodyMarkdown":""},{"url":"/search?q=What+UCaaS+bandwidth+requirements+should+businesses+plan+for%3F","title":"What UCaaS bandwidth requirements should businesses plan for?","bodyMarkdown":""}]},"configJson":{"colSize":2,"columns":2},"noteMarkdown":null,"noteHtml":null,"sortOrder":4}],"citations":[{"title":"How to Switch From On-Prem PBX","url":"https://sangoma.com/blog/how-to-switch-from-on-premises-pbx","excerpt":null,"quoteText":null,"sourceRole":"PRIMARY","verifiedAt":null,"supportsText":null,"domain":"sangoma.com","publisherName":"Sangoma"},{"title":"Migrating from Legacy PBX to UCaaS","url":"https://www.continuant.com/blog/the-ultimate-guide-for-migrating-from-legacy-pbx-to-ucaas","excerpt":null,"quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":null,"supportsText":null,"domain":"continuant.com","publisherName":"Continuant"},{"title":"On-Prem to Cloud VoIP Migration Guide","url":"https://tcinow.com/on-premise-to-cloud-voip-migration-guide","excerpt":null,"quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":null,"supportsText":null,"domain":"tcinow.com","publisherName":"TCI"},{"title":"On-Prem PBX to Cloud: UCaaS and CCaaS","url":"https://www.techmode.com/on-prem-pbx-to-cloud-where-ucaas-and-ccaas-fit-in","excerpt":null,"quoteText":null,"sourceRole":"SUPPORTING","verifiedAt":null,"supportsText":null,"domain":"techmode.com","publisherName":"Techmode"}],"revisions":[],"relatedAnswers":[{"id":"64d09e40-ee5e-4b6f-9c6b-bba0f06d327a","slug":"when-should-a-business-switch-from-voip-to-ucaas","question":"When should a business switch from VoIP to UCaaS?","publishedAt":"2026-06-15T14:29:19.683","confidenceScore":null,"confidenceLabel":null,"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"Switch from VoIP to UCaaS when tool sprawl, remote work, CRM needs, AI features, or a renewal window justify the higher per-user platform cost.","url":"/q/when-should-a-business-switch-from-voip-to-ucaas"},{"id":"cb85d725-4f05-4be8-8196-3a2f82d657e4","slug":"what-ucaas-bandwidth-requirements-should-businesses-plan-for","question":"What UCaaS bandwidth requirements should businesses plan for?","publishedAt":"2026-06-15T14:29:19.417","confidenceScore":null,"confidenceLabel":null,"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"Businesses should budget roughly 100-150 Kbps per concurrent voice call, 2-3 Mbps per HD video participant, low latency and jitter, and peak-hour headroom.","url":"/q/what-ucaas-bandwidth-requirements-should-businesses-plan-for"},{"id":"32c1f9e9-ba62-407a-9fcb-7b9780f43ed7","slug":"what-ucaas-features-matter-most-for-remote-teams","question":"What UCaaS features matter most for remote teams?","publishedAt":"2026-06-15T14:29:19.151","confidenceScore":null,"confidenceLabel":null,"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"Remote teams need one UCaaS app for voice, video, chat, screen sharing, presence, SSO, and AI meeting support, backed by network controls for call quality.","url":"/q/what-ucaas-features-matter-most-for-remote-teams"},{"id":"f7b5d5d8-aadd-4135-b31d-5ff0dbbf934e","slug":"what-ucaas-deployment-model-suits-enterprises-with-hybrid-infrastructure","question":"What UCaaS deployment model suits enterprises with hybrid infrastructure?","publishedAt":"2026-06-15T14:29:18.879","confidenceScore":null,"confidenceLabel":null,"industry":{"id":"ff619d7c-d7d7-485e-a05a-53fba07f33ed","slug":"telecommunications","label":"Telecommunications","description":"Business voice, fiber, UCaaS, and network services"},"topic":{"slug":"ucaas","label":"UCaaS","description":null,"schemaKind":null},"contributor":{"id":"ec39deab-44fe-48d8-9029-fefe993ab85a","slug":"answer-stack","displayName":"AnswerStack","websiteUrl":null},"snippet":"Hybrid enterprises should use hybrid UCaaS: keep regulated voice controls and recording at the edge while shifting meetings, messaging, and cloud services to public UCaaS.","url":"/q/what-ucaas-deployment-model-suits-enterprises-with-hybrid-infrastructure"}],"contributorStats":{"verifiedAnswers":224,"openDisputes":0},"schemaJson":{"@context":"https://schema.org","@type":"Question","name":"How do you migrate from on-premises PBX to UCaaS?","text":"How do you migrate from on-premises PBX to UCaaS?","url":"https://www.answerstack.io/q/how-do-you-migrate-from-on-premises-pbx-to-ucaas","answerCount":1,"datePublished":"2026-06-08T19:57:25.984","author":{"@type":"Organization","name":"AnswerStack","url":"https://www.answerstack.io/contributors/answer-stack"},"about":[{"@type":"Thing","name":"UCaaS"},{"@type":"Thing","name":"Telecommunications"}],"acceptedAnswer":{"@type":"Answer","text":"Migration runs in six phases: audit the existing carrier contract and PBX inventory, validate the network for VoIP, select a UCaaS provider, port numbers, run a parallel pilot, then schedule the production cutover [1][2]. End-to-end timelines run 6 to 16 weeks for mid-market deployments [3]. The single highest-risk step is number porting — most projects schedule it as the final cutover task with the legacy PBX still live as fallback [4]. How to Review the legacy carrier contract Get the contract end date, auto-renewal window (often 30–90 days out), and early-termination fees from your current carrier before doing anything else. Knowing this opens negotiation room with the new provider. Inventory phones, lines, and use cases Document every active phone number per location, distinguish voice from fax/elevator/alarm lines, and capture user preferences: desk phone, softphone, or mobile-only. This sizes the license and hardware order accurately. Validate the network Confirm bandwidth (30 Kbps per concurrent call), turn on QoS to prioritize voice, upgrade switches to PoE if you'll deploy desk phones, and verify the firewall passes SIP traffic without ALG mangling. Select the UCaaS provider and design call flows Match the shortlist against required features (call recording, AI, integrations, compliance). Map every IVR menu, hunt group, and auto-attendant from the legacy PBX into the new platform's admin portal. Submit port orders and run a parallel pilot Open Letters of Authorization to port numbers — porting takes 2 to 6 weeks per carrier. While porting clears, run 10–20 pilot users on the new platform alongside the legacy PBX to surface issues. Cutover and decommission Schedule the production cutover for an off-hours window, validate inbound and outbound calls from every site, keep the legacy PBX powered for 7–14 days as fallback, then decommission hardware and cancel carrier services. Tools and prerequisites Current PBX configuration export Source of call flows, extensions, and number assignments to recreate in UCaaS Carrier contract and CSR (Customer Service Record) Required to validate ownership and submit port orders Network assessment tool Measures bandwidth, jitter, and packet loss before cutover PoE-capable switches Power IP desk phones over the data cable without separate adapters UCaaS admin portal Where you build users, call routing, and auto-attendants in the new platform Project plan and runbook Tracks port dates, pilot users, cutover steps, and rollback triggers Common mistakes Missing the auto-renewal window and getting locked in another year Skipping the network assessment and discovering jitter after cutover Porting numbers before the new platform is tested end-to-end Cutting over during business hours instead of an off-hours window Decommissioning the legacy PBX before a stability soak period Underestimating user training and adoption change-management work Key terms Number porting Workstream Process of transferring existing phone numbers from the legacy carrier to the new UCaaS provider while keeping numbers live. Parallel pilot Workstream Test phase where a subset of users run on UCaaS while the on-prem PBX still handles production traffic. Quality of Service (QoS) Technical dependency Network configuration that prioritizes voice packets over other traffic to keep calls clean during congestion. Power over Ethernet (PoE) Technical dependency Switch capability that powers IP desk phones over the same cable that carries data. Cutover Workstream Scheduled event when production traffic moves from the legacy PBX to UCaaS, usually outside business hours. Related questions How does UCaaS compare to on-premises PBX? /search?q=How+does+UCaaS+compare+to+on-premises+PBX%3F How do you set up UCaaS for a remote team? /search?q=How+do+you+set+up+UCaaS+for+a+remote+team%3F What UCaaS bandwidth requirements should businesses plan for? /search?q=What+UCaaS+bandwidth+requirements+should+businesses+plan+for%3F","url":"https://www.answerstack.io/q/how-do-you-migrate-from-on-premises-pbx-to-ucaas","upvoteCount":0,"datePublished":"2026-06-08T19:57:25.984","dateModified":"2026-06-08T19:57:25.984","author":{"@type":"Organization","name":"AnswerStack","url":"https://www.answerstack.io/contributors/answer-stack"},"citation":[{"@type":"CreativeWork","name":"How to Switch From On-Prem PBX","url":"https://sangoma.com/blog/how-to-switch-from-on-premises-pbx"},{"@type":"CreativeWork","name":"Migrating from Legacy PBX to UCaaS","url":"https://www.continuant.com/blog/the-ultimate-guide-for-migrating-from-legacy-pbx-to-ucaas"},{"@type":"CreativeWork","name":"On-Prem to Cloud VoIP Migration Guide","url":"https://tcinow.com/on-premise-to-cloud-voip-migration-guide"},{"@type":"CreativeWork","name":"On-Prem PBX to Cloud: UCaaS and CCaaS","url":"https://www.techmode.com/on-prem-pbx-to-cloud-where-ucaas-and-ccaas-fit-in"}]}}}