Automatic Multicast Tunneling
Automatic Multicast Tunneling (AMT) provides a method to tunnel multicast data over a unicast network . The tunneling is performed between AMT Relays and AMT Gateways, using UDP (User Datagram Protocol) encapsulation. This enables service providers and their customers to participate in delivering multicast traffic even in the absence of end-to-end multicast connectivity.
Advantages of AMT
The advantages of AMT are:
- Simplicity: Instead of incurring the overhead of manually provisioning, establishing and maintaining GRE tunnels between two locations, the receiving network simply sends AMT advertisements to a well-known any-cast prefix. The rest of the tunnel establishment process is done automatically without the need for additional configuration.
- Resiliency: Because the relay discovery uses an any-cast address, gateways automatically find the closest relay. If that relay becomes unavailable or unreachable, the routing table reconverges on the next closest relay.
Efficiency: AMT allows transit routers to perform flow-based load balancing for more efficient link utilization.
Prerequisites for configuring AMT
The required prerequisites are:
Ensure that the Cisco CRS Router has the CRS-3 line card installed.
- Ensure that you have a Package Installation Envelope (PIE) installed and activated, for running the multicast routing software. For detailed information about optional PIE installation, see Cisco IOS XR Getting Started Guide for the Cisco CRS Router. For running AMT, an mcast PIE must be installed.
Ensure that you are in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Ensure that you know how to apply the generalized interface name with the generalized notation rack/slot/module/port.
Restrictions for AMT
These are the restrictions and limitations for AMT:
Support only for CRS-3 linecards (CRS-MSC-140G and CRS-FP140).
Support for a maximum of 64000 tunnels.
Relay scale highly dependent on the bandwidth of the edge-facing interfaces and the rate of the multicast stream.
Support only for certain features; namely - MTU, QoS, TTL.
No support for ACLs; filtering capability is achieved by accepting or dropping specific gateway addresses.
No support for IPv6 tunnels.