QTECH
Software Configuration Manual
10-129
Mapping relationship between multicast IP address and multicast MAC address
The high-order four bits of the IP multicast address are 1110, representing the multicast ID. Only 23 bits of
the remaining 28 bits are mapped to a MAC address. Thus, five bits of the multicast IP address are lost. As a result,
32 IP multicast addresses are mapped to the same MAC address.
10.2 GMRP Overview
GMRP (GARP Multicast Registration Protocol), based on GARP, is used for maintaining multicast registration
information of the switch. All GMRP-capable switches can receive multicast registration information from other
switches, dynamically update local multicast registration information, and send their own local multicast registration
information to other switches. This information switching mechanism keeps consistency of the multicast information
maintained by every GMRP-supporting device in the same switching network.
A host sends a GMRP Join message, if it is interested in joining a multicast group. After receiving the message,
the switch adds the port on which the message was received to the multicast group, and broadcasts the message
throughout the VLAN where the receiving port resides. In this way, the multicast source in the VLAN gets aware of
the existence of the multicast group member. When the multicast source sends multicast packets to a group, the
switch only forwards the packets to ports connected to the members of that group, thereby implementing Layer 2
multicast in the VLAN.
10.3 GMRP Configuration
10.3.1
GMRP Configuration list
In all configurations, enable global GMRP first before enable GMRP on a port. GMRP Configuration list is
as following :
·
Enable/disable global GMRP
·
Enable/disable GMRP on a port
·
Display GMRP
·
Add/delete multicast that can be dynamic learnt by GMRP
·
Display multicast that can be learnt by GMRP
10.3.2
Enable/disable global GMRP
Please configure it in global configuration mode :
Enable global GMRP
gmrp