24-42
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter24 Configuring IP Multicast Routing
Configuring Optional Multicast Routing Features
Configuring an IP Multicast Boundary
Like TTL thresholds, administratively-scoped boundaries can also be used to limit the forward ing 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 conf igure 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.
Figure 24-12 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 netw ork. 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 two rks. T his bou nda ry prev en ts mul tica st
traffic in the range of 239.128.0.0 through 239.128.255.255 from entering or leaving thei r respec tive
networks.
Figure24-12 Administratively-Scoped Boundaries
You can define an administratively-scoped boundary on a routed in terface for multic ast 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 bou ndary allows the
same multicast group address to be reused in different administ rat ive doma ins .
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 addre s ses can then be reused in domains administered
by different organizations. The addresses would be considered local, not globally unique.
45154
Company XYZ
Engineering Marketing
239.128.0.0/16
239.0.0.0/8