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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-07
Chapter 42 Configuring IP Multicast Routing
Configuring IP Multicast Routing
Figure 42-3 DNS-Based SSM-Mapping
The SSM mapping mechanism that enables the last hop router to join multiple sources for a group can
provide source redundancy for a TV broadcast. In this context, the last hop router provides redundancy
using SSM mapping to simultaneously join two video sources for the same TV channel. However, to
prevent the last hop router from duplicating the video traffic, the video sources must use a server-side
switchover mechanism. One video source is active, and the other backup video source is passive. The
passive source waits until an active source failure is detected before sending the video traffic for the TV
channel. Thus, the server-side switchover mechanism ensures that only one of the servers is actively
sending video traffic for the TV channel.
To look up one or more source addresses for a group that includes G1, G2, G3, and G4, you must
configure these DNS records on the DNS server:
G4.G3.G2.G1 [multicast-domain] [timeout]IN A source-address-1
IN A source-address-2
IN A source-address-n
Refer to your DNS server documentation for more information about configuring DNS resource records,
and go to this URL for additional information on SSM mapping:
http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00801a6d6f.
html
Configuring SSM Mapping
• Configuring Static SSM Mapping, page 42-20 (required)
• Configuring DNS-Based SSM Mapping, page 42-20 (required)
• Configuring Static Traffic Forwarding with SSM Mapping, page 42-21 (optional)
STB host 1 STB host 2 STB host 3
DNS response
DNS server
Reverse DNS lookup
IGMPv2 membership report
(S, G) Join
(S, G) Join
Source
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