Information Technology Reference
In-Depth Information
There are two separate BGP sessions to the provider: an MP-BGP session for the multicast
link (Serial3/0) and a regular BGP session for the unicast link (Serial2/0). The MSDP
session is sourced from the multicast link's interface address. The mBGP NLRI ensures that
the RPF function builds the MDT over the multicast-enabled link. The customer router
injects the local prefix into BGP along with its RP address for remote RPF checks. The
provider does peer-RPF against the e(m)BGP session to the customer. The customer
doesn't need to do a peer-RPF check, because it has only a single MSDP session.
Multiple ISPs, Dedicated Unicast and Multicast
As shown in Figure 11-30, this scenario illustrates that the customer has his or her own RP
and is connected to multiple ISPs. Only one of the ISPs offers multicast service. MSDP is
deployed with mBGP to the ISP offering multicast service. Regular BGP is deployed with
the ISP that does not offer multicast service.
Figure 11-30
Multiple Upstreams, Dedicated Multicast
Multicast Provider
Customer
Network
RP
MSDP Peer
Unicast Provider
The configurations for this scenario are almost identical to the preceding scenario, except
that the BGP sessions go to different providers instead of being attached to different links
on the same router.
The use of mBGP ensures that the RPF resolves to the multicast-enabled ISP, which allows
the MDT to form correctly.
Multiple Upstream ISPs, Redundant Multicast
As shown in Figure 11-31, this scenario illustrates that the customer has his or her own RP
and is multihomed to two ISPs that provide multicast service. The customer wants to use
both ISPs for multicast, using whichever ISP has the best path.
