Configuration Guide User guide

1580 FastIron Configuration Guide
53-1002494-02
DVMRP overview
DVMRP overview
Brocade routers provide multicast routing with the Distance Vector Multicast Routing Protocol
(DVMRP) routing protocol. DVMRP uses Internet Group Membership Protocol (IGMP) to manage the
IP multicast groups.
DVMRP is a broadcast and pruning multicast protocol that delivers IP multicast datagrams to its
intended receivers. The receiver registers the interested groups using IGMP. DVMRP builds a
multicast delivery tree with the sender forming the root. Initially, multicast datagrams are delivered
to all nodes on the tree. Those leaves that do not have any group members send prune messages
to the upstream router, noting the absence of a group. The upstream router maintains a prune
state for this group for the given sender. A prune state is aged out after a given configurable
interval, allowing multicasts to resume.
DVMRP employs reverse path forwarding and pruning to keep source specific multicast delivery
trees with the minimum number of branches required to reach all group members. DVMRP builds
a multicast tree for each source and destination host group.
NOTE
DVMRP is supported only on FastIron SX devices.
Initiating DVMRP multicasts on a network
Once DVMRP is enabled on each router, a network user can begin a video conference multicast
from the server on R1. Multicast Delivery Trees are initially formed by source-originated multicast
packets that are propagated to downstream interfaces as seen in Figure 178. When a multicast
packet is received on a DVMRP-capable router interface, the interface checks its DVMRP routing
table to determine whether the interface that received the message provides the shortest path
back to the source. If the interface does provide the shortest path, the interface forwards the
multicast packet to adjacent peer DVMRP routers, except for the router interface that originated the
packet. Otherwise, the interface discards the multicast packet and sends a prune message back
upstream. This process is known as reverse path forwarding.
In Figure 178, the root node (R1) is forwarding multicast packets for group 229.225.0.2 that it
receives from the server to its downstream nodes, R2, R3, and R4. Router R4 is an intermediate
router with R5 and R6 as its downstream routers. Because R5 and R6 have no downstream
interfaces, they are leaf nodes.
The receivers in this example are those workstations that are resident on routers R2, R3, and R6.
Brocade#show ip pim mcache
1 (10.10.10.18 226.0.1.56) in v10 (e1), cnt=2
Source is directly connected
Sparse Mode, RPT=0 SPT=1 REG=1 MSDP Adv=0 MSDP Create=0
fast=0 slow=0 pru=1 graft age drop
age=0s up-time=2m HW=1 L2-vidx=8191