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Appendix B: WAN Configuration Example
This appendix provides a sample configuration for multicasting over a generic routing encapsulation (GRE) tunnel as an example of how to
configure an Endura network using WAN connectivity. Much of the information in this appendix is derived from the online document titled
Multicasting Over a GRE Tunnel, published by Cisco Systems
®
. To view this document, go to or click http://www.cisco.com/en/US/tech/tk828/
technologies_configuration_example09186a00801a5aa2.shtml.
In an Endura application scenario, where you want to extend an existing Endura network across a network that does not support multicast, it is
recommended that you configure a GRE tunnel to send multicast traffic between routers. In this case, the GRE tunnel is required because the
multicast source and receiver are separated by an IP cloud that is not configured to support IP multicast traffic. In such network scenarios,
configuring a tunnel across an IP cloud with PIM will allow multicast packets to be exchanged between the source and receiver.
This appendix describes the configuration, verification, and related issues pertaining to multicasting over a GRE tunnel. The information
presented in this appendix was created from devices in a specific lab environment. All of the devices used in this appendix started with a cleared
(default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.
NETWORK CONFIGURATION OVERVIEW
As shown in Figure 15, the multicast source (10.1.1.1) is connected to R102 and is configured for multicast group 239.1.1.20. The multicast
receiver (10.2.2.3) is connected to R104 and is configured to receive multicast packets for group 239.1.1.20. Separating R102 and R104 is an
IP cloud, which is not configured for multicast routing.
Figure 15. Sample Endura Network Over a WAN
A tunnel is configured between R102 to R104 sourced with their loopback interfaces. The ip pim sparse-dense mode command is configured on
tunnel interfaces and multicast-routing is enabled on R102 and R104. Sparse-dense mode configuration on the tunnel interfaces allows sparse-
mode or dense-mode packets to be forwarded over the tunnel depending on rendezvous point (RP) configuration for the group.
• For dense mode: With PIM dense mode configured over the tunnel, an ip mroute 10.1.1.0 255.255.255.0 tunnel 0 command is configured
on R104 to ensure a successful RPF for multicast source address 10.1.1.1. Incoming (10.1.1.1, 239.1.1.20) multicast packets over Tunnel0
(Tu0) are checked for Reverse Path Forwarding (RPF) using this mroute statement. After a successful check, the multicast packets are
forwarded to outgoing interface list (OIL) interfaces.
• For sparse mode: With PIM sparse mode configured over the tunnel, ensure that the following points are addressed:
– For a successful RPF verification of multicast traffic flowing over the shared tree (*,G) from RP, an ip mroute rp-address nexthop
command needs to be configured for the RP address, pointing to the tunnel interface.
Assuming R102 to be the RP (RP address 2.2.2.2) in this case, the mroute would be the ip mroute 2.2.2.2 255.255.255.255 tunnel 0
command, which ensures a successful RPF check for traffic flowing over the shared tree.
– For a successful RPF verification of multicast (S,G) traffic flowing over the Shortest Path Tree (SPT), an ip mroute source-address
nexthop command needs to be configured for the multicast source, pointing to the tunnel interface.
In this case, when SPT traffic is flowing over tunnel interface an ip mroute 10.1.1.0 255.255.255.0 tunnel 0 command is configured on
R104 to ensure a successful RPF verification for incoming (10.1.1.1, 239.1.1.20) multicast packets over the Tu0 interface.
The sample configuration files for R102 and R104 are described in the following sections:
• City A Router (R102) Configuration File on page 32
• City B Router (R104) Configuration File on page 33
IP CLOUD
192.168.23.0
192.168.24.0 TUNNEL
.1
.2
.1 Tu0 Tu0
.2
.2
.3
10.2.2.0
ENDURA
ENCODER
MULTICAST SOURCE
GRP: 239.1.1.20
10.1.1.0
CITY A ROUTER
(R102)
192.168.34.0
CITY B ROUTER
(R104)
ENDURA
WORKSTATION
MULTICAST RECEIVER
GRP: 239.1.1.20