HPE 5820X Series, Configuration Manual

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Concepts in multicast traceroute
•
Last-hop router
—If one of the interfaces of a router connects to the subnet that contains the
given destination address, and if the router can forward multicast streams from the given
multicast source onto that subnet, that router is called the "last-hop router." The given
destination address and the given multicast source are specified in the
mtracert
command.
•
First-hop router
—The router that directly connects to the multicast source is called the
"first-hop router."
•
Querier
—The router that sends multicast traceroute requests is called the "querier."
Introduction to multicast traceroute packets
A multicast traceroute packet is a special IGMP packet that is different from common IGMP packets.
The difference lies in that its IGMP Type field is set to 0x1F or 0x1E and its destination IP address is
a unicast address. The following types of multicast traceroute packets are available:
•
Query
—Its IGMP Type field set to 0x1F.
•
Request
—Its IGMP Type field set to 0x1F.
•
Response
—Its IGMP Type field set to 0x1E.
Process of multicast traceroute
1.
The querier sends a query to the last-hop router.
2.
After receiving the query, the last-hop router turns the query packet into a request packet by
adding a response data block to the end of the packet. The response data block contains its
interface addresses and packet statistics. The last-hop router then forwards the request packet
through unicast to the previous hop for the given multicast source and group.
3.
From the last-hop router to the multicast source, each hop adds a response data block to the
end of the request packet and unicasts it to the previous hop.
4.
When the first-hop router receives the request packet, it changes the packet type to indicate a
response packet. Then, it sends the completed packet through unicast to the querier.
Configuration task list
Task Remarks
Enabling IP multicast routing Required.
Configuring multicast
routing and forwarding
Configuring static multicast routes Optional.
Configuring a multicast routing policy Optional.
Configuring a multicast forwarding range Optional.
Configuring the multicast forwarding table size Optional.
Tracing a multicast path Optional.
Enabling multicast optimization Optional.