<?xml version="1.0" encoding="US-ASCII"?>
<!-- Generated by CompSci Transform (tm) - http://www.compsciresources.com -->
<!-- Created: Wed Apr 15 22:28:15 UTC 2026 -->
<linkbase xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:xbrldt="http://xbrl.org/2005/xbrldt">
  <roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#IndividualsOnly" roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly"/>
  <roleRef xlink:type="simple" xlink:href="rbbn-20251231.xsd#rbbn_r_AdditionalDimensions" roleURI="http://ribboncommunications.com/role/AdditionalDimensions"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all"/>
  <definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <loc xlink:type="locator" xlink:label="ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllIndividualsMember"/>
    <loc xlink:type="locator" xlink:label="rbbn_BruceMcClellandMember" xlink:href="rbbn-20251231.xsd#rbbn_BruceMcClellandMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ecd_AllIndividualsMember" xlink:to="rbbn_BruceMcClellandMember" order="2" xbrldt:closed="true"/>
  </definitionLink>
<!-- [WMV6][q0TspjmbIY95gfdm0HU3M4rnbkGZkLLv+LNapJYEr3olKCotkUcPjxhHxquYr3ykpmvs/L2JWka8ogi7skMWkAUraeqs2amHc3GRT5dpfjFl6EAKWC29EnSDaTXaXgXHMKH3rBAAcHnyplsZ/k4oXivQc7qOuRlj9ZeA/cdX3ctMkUTiRLAfc3NUXncIA/wtvjlUcaWaMJvIZGCEoMZHwYqE2//X0NmMYzWW031mNX+iXsCr55HxPoIdOZP2BEgt9v7vQ9BNlTBmMDTvOpG7nx/Lc3SHiLHOuMQQCnWtpuaVbcEODAk5goATA/a57U9bAmu4mmZF9QMb] CSR-->
  <definitionLink xlink:role="http://ribboncommunications.com/role/AdditionalDimensions" xlink:type="extended"/>
</linkbase>
