(Optional) Configuring a Static Router Port

A router port is located on a Layer 2 device and connects to an upstream Layer 3 device (a multicast router or Layer 3 switch). When IGMP snooping is enabled in a VLAN, all interfaces in this VLAN learn forwarding entries from multicast protocol packets. When an interface receives IGMP Query messages or Protocol Independent Multicast (PIM) Hello messages, the Layer 2 device sets this interface as a dynamic router port. A router port provides the following functions:

• Receives multicast data from the upstream device.
• Forwards IGMP Report/Leave messages. IGMP Report/Leave messages received in a VLAN are forwarded only to router ports in the VLAN.

A dynamic router port has an aging time. If a dynamic router port does not receive an IGMP Query or a PIM Hello message before the aging time expires, the device deletes the port from the router port list. To enable an interface to forward IGMP Report/Leave messages to the upstream querier for a long time, configure the interface as a static router port.

On a ring network running IGMP snooping, if the downstream port of a device is configured as a static router port, downstream ports of all devices on the ring network must be configured as static router ports. Otherwise, multicast traffic cannot be forwarded normally if the Layer 2 network topology changes. Therefore, it is not recommended to configure downstream ports as static router ports.