Multicast Tunnel Interfaces - Cisco 7604 Configuration Manual

Chapter 25 Configuring IPv4 Multicast VPN Support
Figure 25-2 Initializing the Data MDT
Customer 1
San Jose Site
The CE router (CE1a) starts sending the multicast data to the associated PE router (PE1), which
recognizes that the multicast data exceeds the bandwidth threshold at which a data MDT should be
created. PE1 then creates a data MDT and sends a message to all routers using the default MDT that
contains information about the data MDT.
Approximately three seconds later, PE1 begins sending the multicast data for that particular stream using
the data MDT. Because only PE2 has receivers who are interested in this source, only PE2 joins the data
MDT and receives traffic on it.

Multicast Tunnel Interfaces

The PE router creates a multicast tunnel interface (MTI) for each multicast VRF (MVRF) in the
multicast domain. The MVRF uses the tunnel interface to access the multicast domain to provide a
conduit that connects an MVRF and the global MVRF.
On the router, the MTI is a tunnel interface (created with the interface tunnel command) with a class D
multicast address. All PE routers that are configured with a default MDT for this MVRF create a logical
network in which each PE router appears as a PIM neighbor (one hop away) to every other PE router in
the multicast domain, regardless of the actual physical distance between them.
The MTI is automatically created when an MVRF is configured. The BGP peering address is assigned
as the MTI interface source address, and the PIM protocol is automatically enabled on each MTI.
OL-4266-08
Multicast Local multicast
sender recipient
CE1a CE1b
3. PE1 receives join
PE1
request and asks
CE1a to begin
sending data
P1
P4
PE4
CE4
Customer 2
Houston Site
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
1. Remote enterprise
client issues
join request
2. PE2 sends join
request along
default MDT
PE2
P2
MPLS Core
P3
PE3
Customer 1
Dallas Site
Understanding How MVPN Works
CE2
Customer 1
New York Site
CE3
25-5