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Chapter44 Configuring IP Multicast Routi ng Configuring Optional Multicast Routing Features
Configuring an IP Multicast Boundary
Administratively-scoped boundaries can be used to limit the forwarding of multicast traffic outside of a
domain or subdomain. This approach uses a special range of multicast addresses, called
administratively-scoped addresses, as the boundary mechanism. If you configure an
administratively-scoped boundary on a routed interface, multicast traffic whose multicast group
addresses fall in this range can not enter or exit this interface, thereby providing a firewall for multicast
traffic in this address range.
Note Multicast boundaries and TTL thresholds control the scop ing of mu ltic as t dom ain s; however, TTL
thresholds are not supported by the switch. You should use multicast boundaries instead of TTL
thresholds to limit the forwarding of multicast traffic outside of a domain or a subdomain.
Figure 44-6 shows that Company XYZ has an administratively-scoped boundary set for the multicast
address range 239.0.0.0/8 on all routed interfaces at the perimeter of its net work. This boundary prevents
any multicast traffic in the range 239.0.0.0 through 239.255.255.255 from entering or leaving the
network. Similarly, the engineering and marketing departments have an administratively-scoped
boundary of 239.128.0.0/16 around the perimeter of their ne tworks . This bou ndary pr events multi cast
traffic in the range of 239.128.0.0 through 239.128.255.255 from e nter ing or leaving thei r resp ec tive
networks.
Figure44-6 Administratively-Scoped Boundaries
You can define an administratively-scoped boundary on a routed interface for multicast group addresses.
A standard access list defines the range of addresses affected. When a boundary is defined, no multicast
data packets are allowed to flow across the boundary from either direction. The boundary allows the
same multicast group address to be reused in different admi nist rat ive domains.
The IANA has designated the multicast address range 239.0.0.0 to 239.255.255.255 as the
administratively-scoped addresses. This range of addresses can then be reused in domains ad ministered
by different organizations. The addresses would be considered local, not globally unique.
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Company XYZ
Engineering Marketing
239.128.0.0/16
239.0.0.0/8