Which message type is constructed and sent from an MSDP router to its MSDP peers when it
receives a PIM register message (knowing that the MSDP router is also configured as an RP for
the PIM domain)?
A.
Source-Active Message
B.
PIM Join
C.
PIM Hello
D.
MSDP Register
Explanation:
Information About MSDP
You can use the Multicast Source Discovery Protocol (MSDP) to exchange multicast source
information between multiple BGP-enabled Protocol Independent Multicast (PIM) sparse-mode
domains.
When a receiver for a group matches the group transmitted by a source in another domain, therendezvous point (RP) sends PIM join messages in the direction of the source to build a shortest
path tree. The designated router (DR) sends packets on the source-tree within the source domain,
which may travel through the RP in the source domain and along the branches of the source-tree
to other domains. In domains where there are receivers, RPs in those domains can be on the
source-tree. The peering relationship is conducted over a TCP connection.
Figure 6-1 shows four PIM domains. The connected RPs (routers) are called MSDP peers
because each RP maintains its own set of multicast sources. Source host 1 sends the multicast
data to group 224.1.1.1. On RP 6, the MSDP process learns about the source through PIM
register messages and generates Source-Active (SA) messages to its MSDP peers that contain
information about the sources in its domain. When RP 3 and RP 5 receive the SA messages, they
forward them to their MSDP peers. When RP 5 receives the request from host 2 for the multicast
data on group 224.1.1.1, it builds a shortest path tree to the source by sending a PIM join
message in the direction of host 1 at 192.1.1.1.
When you configure MSDP peering between each RP, you create a full mesh. Full MSDP meshing
is typically done within an autonomous system, as shown between RPs 1, 2, and 3, but not across
autonomous systems.
You use BGP to do loop suppression and MSDP peer-RPF to suppress looping SA messages. For
more information about mesh groups, see the “MSDP Mesh Groups” section.
NoteYou do not need to configure MSDP in order to use Anycast-RP (a set of RPs that can perform
load balancing and failover) within a PIM domain. For more information, see the “Configuring a
PIM Anycast-RP Set” section.
For detailed information about MSDP, see RFC 3618.
http://www.cisco.com/en/US/docs/switches/datacenter/sw/5_x/nxos/multicast/configuration/guide/msdp.html
