The PIMv2 Assert Message Format
The PIMv2 Assert message, the format of which is illustrated in Figure 5-68, is used to elect a designated forwarder on multiaccess networks. When a PIM router receives a multicast packet on an interface that is on the outgoing interface for the packet's group, the router assumes that there must be another router connected to that data link forwarding for the group. The router sends an Assert so that other routers sharing the multiaccess network can decide which of them will forward packets for the group.
Figure 5-68 The PIMv2 Assert Message Format
32 bits
Version
Reserved
Encoded Group Address
Encoded Unicast Source Address
Metric Preference
The fields for the PIMv2 Assert message are defined as follows:
• Encoded Group Address is the multicast IP destination address of the packet that triggered the Assert.
• Encoded Unicast Source Address is the IP source address of the multicast packet that triggered the Assert.
• Metric Preference is a preference value assigned to the unicast routing protocol that provided the route to the source. This value is used in the same way an administrative distance is used, to provide a consistent metric when comparing routes from diverse routing protocols.
• Metric is the metric associated with the route to the source in the originator's unicast routing table.
Continue reading here: Configuring IP Multicast Routing
Was this article helpful?