PnP Auto Provisioning IP Phone Multicast Debug

To enable PortSIP PBX to answer PnP provisioning requests, all of the following requirements must be met:

• The PortSIP PBX must be able to join the multicast group

• The IP phone and PBX must be on the same local LAN subnet

• The network switch/router must support multicast

• The IP phone must support PnP provisioning

❗ Important PnP provisioning relies on SIP multicast discovery. If any requirement above is not satisfied, automatic discovery will fail and the phone must be provisioned manually.

---

PortSIP PBX Must Be Able to Join the Multicast Group

Depending on the network interface order, PortSIP PBX may not be able to listen for multicast events.

❗ Important Unused LAN adapters, Wi-Fi, and Bluetooth interfaces must be disabled. These interfaces cannot be used to join multicast events and may prevent the PBX from listening on the correct network interface.

---

Verify Multicast Membership on Windows

1. Open the Command Prompt as Administrator.

2. Run the following command:

   netsh interface ipv4 show join

3. Verify that the multicast address 224.0.1.75 appears on the correct network interface.

If your interface does not list this address, the PBX is not ready for PnP provisioning.

---

Fix Multicast Issues on Windows (Interface Metric Adjustment)

1. Open Control Panel > Network and Internet > Network Connections.

2. Right-click the active network adapter and select Properties.

3. Select Internet Protocol Version 4 (TCP/IPv4) → Properties → Advanced.

4. Edit the Default Gateway Metric and try the following values one at a time:

   • 1

   • 10

   • 12

   • 15

   • 20

5. After each change:

   • Reboot the server

   • Re-run netsh interface ipv4 show join

   • Confirm the multicast join appears

---

Verify Multicast Membership on Linux

1. Connect to the PBX server via SSH.

2. Switch to the root user.

3. Run the following command:

   netstat -g

4. Verify that sip.mcast.net is listed on the active application interfaces.

If it is not listed, the PBX is not receiving multicast traffic and cannot support PnP discovery.

---

IP Phone and PBX Must Be in the Same Local LAN Subnet

PnP provisioning requires multicast message exchange, which does not cross subnets.

Supported Example (Will Work)

• PBX: 192.168.1.1 / 255.255.255.0

• Phone: [phone]

Unsupported Example (Will Not Work)

• PBX: 192.168.0.1 / 255.255.255.0

• Phone: [phone] (different subnet)

❗ Important VLANs, routed networks, or NAT boundaries will prevent multicast discovery. Phones in these environments must be provisioned using manual provisioning links.

---

Network Infrastructure Must Support Multicast

• Switches and routers must allow multicast traffic

• IGMP snooping or multicast filtering must be configured correctly

• Multicast must not be blocked by firewall rules

❗ Best Practice In enterprise environments, verify multicast behavior with your network team before deploying PnP at scale.

---

IP Phone Must Support PnP Provisioning

The IP phone firmware must support PnP multicast announcements.

❗ Important Some older phone firmware versions do not fully implement PnP discovery. If discovery fails and all other requirements are met, upgrade the phone to the latest supported firmware and retry.

---

Summary

For successful PnP provisioning:

• The PBX must correctly join the multicast group

• Phones and PBX must share the same LAN subnet

• The network must permit multicast traffic

• IP phones must support PnP and run compatible firmware

When these conditions are met, IP phones will be discovered automatically and can be provisioned quickly through the PortSIP PBX Web Portal.