Configuring Multicast Forwarding Table Size - 3Com MSR 50 Series Configuration Manual

Configuring Multicast
Forwarding Table Size
Specifying boundary interfaces, which form a closed multicast forwarding area,
■
or
Setting the minimum time to live (TTL) value required for a multicast packet to
■
be forwarded.
You can configure a forwarding boundary specific to a particular multicast group
on all interfaces that support multicast forwarding. A multicast forwarding
boundary sets the boundary condition for the multicast groups in the specified
range. If the destination address of a multicast packet matches the set boundary
condition, the packet will not be forwarded. Once a multicast boundary is
configured on an interface, this interface can no longer forward multicast packets
(including packets sent from the local device) or receive multicast packets.
You can configure the minimum TTL required for a multicast packet to be
forwarded on all interfaces that support multicast forwarding. Before being
forwarded from an interface, every multicast packet (including multicast packet
from the local device) is subject to a TTL check:
If the TTL value of the packet (already decremented by 1 on this router) is larger
■
than the minimum TTL value configured on the interface, the packet will be
forwarded.
If the TTL value of the packet is smaller than or equal to the minimum TTL value
■
configured on the interface, the packet will be discarded.
Follow these steps to configure a multicast forwarding range:
To do...
Enter system view
Enter interface view
Configure a multicast
forwarding boundary
Configure the minimum
packet TTL required for a
multicast packet to be
forwarded
Too many multicast routing entries can exhaust the router's memory and thus
result in lower router performance. Therefore, the number of multicast routing
entries should be limited. You can set a limit on the number of entries in the
multicast routing table based on the actual networking situation and the
performance requirements. In any case, the number of route entries must not
exceed the maximum number allowed by the system.
If the configured maximum number of downstream nodes (namely, the maximum
number of outgoing interfaces) for a routing entry in the multicast forwarding
table is smaller than the current number, the downstream nodes in excess of the
configured limit will not be deleted immediately; instead they must be deleted by
the multicast routing protocol. In addition, newly added downstream nodes
cannot be installed to the routing entry in the forwarding table.
Configuring Multicast Routing and Forwarding
Use the command...
system-view
interface interface-type
interface-number
multicast boundary
group-address { mask |
mask-length }
multicast minimum-ttl
ttl-value
1105
Remarks
-
-
Required
No forwarding boundary by
default
Optional
1 by default