Scoping - Hirschmann MACH 4000 User Manual

Multicast Routing

9.4 Scoping

In the Multicast transmission, the protocol provides two options for limiting
the expansion of the Multicast data stream:
Multicast Address Scoping / Boundary
In the Multicast Address Scoping, the administrator assigns a Multicast IP
address range to a router interface
blocks the Multicast data streams with addresses within this address
range.
Example:
ip mcast boundary 239.193.122.0 255.255.255.0
In this example, the router interface blocks Multicast data streams with a
Multicast IP address in the range 239.193.122.0-239.193.122.255.
TTL Scoping
Every Multicast data packet contains a TTL (Time To Live). The TTL is a
counter which each router de-increments when it transmits a Multicast
data packet.
In TTL Scoping, the administrator assigns a TTL threshold to an interface.
The router interface blocks every Multicast data packet for which the TTL
is below the TTL threshold.
Example:
ip multicast ttl threshold 64
In this example, the router interface blocks Multicast data streams with a
TTL whose value is less than 64.
TTL Scope
0 Restricted to the same host
1 Restricted to the same subnet
< 32 Restricted to a particular location, organization or department
< 64 Restricted to the same region
< 128 Restricted to the same continent
< 255 Unrestricted, global
Table 15: Usual scope for TTLs
Routing L3P
Release 4.0 11/07
(see table 11). The router interface
9.4 Scoping
107