SSM mapping enables the last hop router to determine the source addresses either by a statically configured
table on the router or by consulting a DNS server. When the statically configured table is changed, or when
the DNS mapping changes, the router will leave the current sources associated with the joined groups.
Related Topics
Configuring Static SSM Mapping(CLI), on page 270
Verifying SSM Mapping Configuration and Operation, on page 276
Configuring Basic IP Multicast Routing, on page 290
Configuring DNS-Based SSM Mapping(CLI), on page 271
Verifying SSM Mapping Configuration and Operation, on page 276
Configuring Basic IP Multicast Routing, on page 290
Configuring Static Traffic Forwarding with SSM Mapping (CLI), on page 274
Static SSM Mapping
SSM static mapping enables you to configure the last hop router to use a static map to determine the sources
sending to groups. Static SSM mapping requires that you configure access lists (ACLs) to define group ranges.
The groups permitted by those ACLs then can be mapped to sources using the ip igmp static ssm-map global
configuration command.
You can configure static SSM mapping in smaller networks when a DNS is not needed or to locally override
DNS mappings that may be temporarily incorrect. When configured, static SSM mappings take precedence
over DNS mappings.
Related Topics
Configuring Static SSM Mapping(CLI), on page 270
Verifying SSM Mapping Configuration and Operation, on page 276
Configuring Basic IP Multicast Routing, on page 290
DNS-Based SSM Mapping
DNS-based SSM mapping enables you to configure the last hop router to perform a reverse DNS lookup to
determine sources sending to groups (see the figure below). When DNS-based SSM mapping is configured,
the router constructs a domain name that includes the group address G and performs a reverse lookup into the
DNS. The router looks up IP address resource records (IP A RRs) to be returned for this constructed domain
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3.6E (Catalyst 3850 Switches)
OL-32598-01 265
Configuring SSM
SSM Mapping Overview
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