A Cisco VoIP developer is responsible for designing, implementing, and maintaining Voice over IP (VoIP) telephony systems for businesses. They work with Cisco technologies to create systems that allow for audio communication over the internet. Their tasks include setting up VoIP infrastructures, integrating them with existing networks, troubleshooting any issues, and ensuring network security. They may also develop and implement new VoIP features or applications to improve communication efficiency. Additionally, they often collaborate with other IT professionals to coordinate system-wide updates or modifications and provide technical support to end-users.