Enterasys C5G124-24 User Manual

Using Multicast in Your Network
19-8 Configuring Multicast
A DVMRP device forwards multicast packets first by determining the upstream interface, and
then by building the downstream interface list. If a downstream router has no hosts for a multicast
stream, it sends a prune message to the upstream router. If the upstream router’s outbound list is
now empty, it may send a prune message to its upstream router.
If a downstream device has pruned a multicast group that a host would like to now receive, the
downstream device must send a DVMRP graft message to its upstream device. The DVMRP graft
will traverse the source-specific multicast delivery tree to the device that is receiving this stream.
As shown in the following example output, the Mroute table displays the incoming interface IP
address, the multicast group address, the uptime of the stream, the address of the upstream
neighbor, and the upstream and downstream VLANs.
System(su)->router#show ip mroute
Active IP Multicast Sources
Flags: D - Dense, S - Sparse, C - Connected, L - Local,P - Pruned, R - RP-bit set,
F - Register flag, T - SPT-bit set,Outgoing interface flags: H - Hardware switched
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode
Source Network : 192.168.111.10
Source Mask : 0.0.0.0
MultiCast Group : 239.1.8.9
Uptime : 6336
Upstream Neighbor: 0.0.0.0
Upstream Vlan : 111
Downstream Vlans : 8
Source Network : 192.168.111.10
Source Mask : 0.0.0.0
MultiCast Group : 239.1.7.105
Uptime : 6336
Upstream Neighbor: 0.0.0.0
Upstream Vlan : 111
Downstream Vlans : 8
Source Network : 192.168.111.10
Source Mask : 0.0.0.0
MultiCast Group : 239.1.8.169
Uptime : 6582
Upstream Neighbor: 0.0.0.0
Upstream Vlan : 111
Downstream Vlans : 8
Source Network : 192.168.111.10
Source Mask : 0.0.0.0
MultiCast Group : 239.1.4.173
Uptime : 6582
Upstream Neighbor: 0.0.0.0
Upstream Vlan : 111
Downstream Vlans : 8
In this example, the device is receiving multicast streams for groups 239.1.8.9, 239.1.7.105,
239.1.8.169, and 239.1.4.173 from IP address 192.168.111.10 on the incoming interface VLAN 8.
Prune Messages
If a device receives a datagram that has no IGMP group members present, and all the downstream
networks are leaf networks, the device sends a prune packet upstream to the source tree.
When sending a prune upstream, the device:

Enterasys C5G124-24 Specifications

General

Brand	Enterasys
Model	C5G124-24
Category	Switch
Language	English