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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.
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Efficiency: AMT allows transit routers to perform flow-based load balancing for more efficient link
utilization.
Prerequisites for configuring AMT
The required prerequisites are:
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Ensure that the Cisco CRS Router has the CRS-3 line card installed.
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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.
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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:
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Support only for CRS-3 linecards (CRS-MSC-140G and CRS-FP140).
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Support for a maximum of 64000 tunnels.
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Relay scale highly dependent on the bandwidth of the edge-facing interfaces and the rate of the multicast
stream.
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Support only for certain features; namely - MTU, QoS, TTL.
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No support for ACLs; filtering capability is achieved by accepting or dropping specific gateway addresses.
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No support for IPv6 tunnels.
Cisco IOS XR Multicast Configuration Guide for the Cisco CRS Router, Release 5.2.x
194
Implementing Automatic Multicast Routing:
Prerequisites for configuring AMT