Multicast Traceroute - H3C S3610-28P Operation Manual

Operation Manual – Multicast Protocol
H3C S3610&S5510 Series Ethernet Switches
unicast RPF route and the optimal multicast static route respectively from the routing
tables, and uses one of them as the RPF route after comparison.
Figure 8-2 Multicast static route
As shown in
neighbor on the path back to Source is Switch A and the multicast information from
Source travels along the path from Switch A to Switch C, which is the unicast route
between the two Switchs; with a static route configured on Switch C and Switch B as
Switch C's RPF neighbor on the path back to Source, the multicast information from
Source travels from Switch A to Switch B and then to Switch C.

8.1.4 Multicast Traceroute

The multicast traceroute utility is used to trace the path that a multicast stream flows
down from the multicast source to the last-hop router.
I. Concepts in multicast traceroute
1) Last-hop router: If a router has one of its interfaces connecting to the subnet the
given destination address is on, and if the router is able to forward multicast
streams from the given multicast source onto that subnet, that router is called
last-hop router.
2) First-hop router: the router that directly connects to the multicast source.
3) Querier: the router requesting the multicast traceroute.
II. Introduction to multicast traceroute packets
A multicast traceroute packet is a special IGMP packet, which differs from common
IGMP packets in that its IGMP Type field is set to 0x1F or 0x1E and that its destination
IP address is a unicast address. There are three types of multicast traceroute packets:
Query, with the IGMP Type field set to 0x1F,
Figure 8-2, when no multicast static route is configured, Switch C's RPF
Chapter 8 Multicast Routing and Forwarding
8-5
Configuration