/mcpport. 00-00-00-00-00- 00 Router MAC Leave Unassig n router port. Mcast MAC 00-00-00-00-00- 00 Leave Delete group. 00-00-00-00-00- 00 00-00-00-00-00- 00 Leave Delete all groups. Learning Router Ports The switch needs to be aware of all router ports so that they are automatically added to any newly created multicast entries. The switch learns router ports when it receives a CGMP Join to GDA 00- 00-00-00-00-00 with Router MAC USA (third type of message in the table). These messages are generated by the router on all interfaces configured to run CGMP. There is also a static method, however, for configuring router ports on the switch. Joining a Group with CGMP A new client requests to receive traffic for a GDA, so the client sends an IGMP Membership report message. G The router receives the IGMP report, processes it, and sends a CGMP message to the switch. The router copies the destination MAC address into the GDA field of the CGMP Join, and copies the source MAC address into the USA of the CGMP join. It then sends it back to the switch. G A switch with CGMP enabled needs to listen to the CGMP 01-00-0c-dd-dd-dd addresses. The processor of the switch looks into the CAM table for the USA. Once the USA is seen in the CAM table, the switch knows which port the USA is located on, and does one of the following:Creates a new static entry for the GDA and links the USA port to it along with all router ports.Adds the USA port to the list of the ports for this GDA (if the static entry already exists). G Leaving a Group With CGMP Static entries learned with CGMP are permanent, unless a spanning tree topology change occurs in the VLAN, or the router sends one of the last CGMP Leave messages in the previous table. When IGMPv1 is the host, do not send IGMP Leave messages. The router only sends Leave messages if it does not receive a reply to three consecutive IGMP queries. This means that no port is deleted from a group if any users are still interested in that group. With the introduction of IGMPv2 and the presence of IGMP Leave, Cisco added to the original CGMP specification (CGMPv2). This addition is called CGMP Fast-Leave. CGMP Fast-Leave processing allows the switch to detect IGMPv2 Leave messages sent to the all- router multicast address (224.0.0.2) by hosts on any of the supervisor engine module ports. When the supervisor engine module receives a Leave message, it starts a query-response timer and sends a message on the port on which that leave was received to determine if there is still a host