3com S7906E 설치 설명서

 

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Multicast packets do not travel without a boundary in a network. The multicast data corresponding to 

each multicast group must be transmitted within a definite scope. Presently, you can define a multicast 

forwarding range by specifying boundary interfaces, which form a closed multicast forwarding area. 

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.  

Follow these steps to configure a multicast forwarding range:  

Enter system view 

— 

Enter interface view 

interface interface-type 
interface-number 

— 

Configure a multicast 
forwarding boundary 

multicast boundary 
group-address { mask | 
mask-length } 

Required 

No forwarding boundary by 
default  

 

The router maintains the corresponding forwarding entry for each multicast packet it receives. 

Excessive multicast routing entries, however, can exhaust the router’s memory and thus result in lower 

router performance. You can set a limit on the number of entries in the multicast forwarding table based 

on the actual networking situation and the performance requirements. If the configured maximum 

number of multicast forwarding table entries is smaller than the current value, the forwarding entries in 

excess will not be immediately deleted; instead they will be deleted by the multicast routing protocol 

running on the router. The router will no longer add new multicast forwarding entries until the number of 

existing multicast forwarding entries comes down below the configured value.  

When forwarding multicast traffic, the router replicates a copy of the multicast traffic for each 

downstream node and forwards the traffic, and thus each of these downstream nodes forms a branch of 

the multicast distribution tree. You can configure the maximum number of downstream nodes (namely, 

the maximum number of outgoing interfaces) for a single entry in the multicast forwarding table to 

lessen burden on the router for replicating multicast traffic. If the configured maximum number of 

downstream nodes for a single multicast forwarding entry is smaller than the current number, the 

downstream nodes in excess will not be deleted immediately; instead they must be deleted by the 

multicast routing protocol. The router will no longer add new multicast forwarding entries for newly 

added downstream nodes until the number of existing downstream nodes comes down below the 

configured value.