Using Multicast in Your Network
19-6 Configuring Multicast
DVMRP routing is implemented on Enterasys devices as specified in RFC 1075 and draft-ietf-idmr-
dvmrp-v3-10.txt.
Enterasys devices support the following DVMRP components:
• Probe Messages for neighbor discovery
• Route Table for maintaining routes to all DVRMP networks
• Route Reports for route exchange with adjacent devices
• Mroute Table for maintaining per-source-group multicast trees
• Prune Messages for terminating multicast delivery trees
• Graft Messages for re-adding pruned multicast delivery trees
Probe Messages
Each DVMRP-enabled interface transmits multicast probe packets to inform other DVMRP
routers that it is operational. Probe messages are sent every 10 seconds on every interface running
DVMRP. These messages provide:
• A mechanism for DVMRP devices to locate each other. Probe messages contain a list of the
neighbors detected for each enabled interface. If no neighbors are found, the network is
considered to be a leaf network.
• A mechanism for DVMRP devices to determine the capabilities of neighboring devices.
Probe messages contain flags about neighbors’ DVMRP capabilities and version compliance.
• A keep-alive function for quickly detecting neighbor loss. If a probe message from an
adjacent neighbor is not seen within 35 seconds, the neighbor is timed out.
Route Table
Each DVMRP-enabled device builds a DVMRP route table to maintain routes to all networks
involved in DVMRP routing. As shown in the following example output, the DVMRP route table
contains destination and neighbor addresses, metric value (in brackets), expiration time (currently
not supported in the firmware), up-time (in seconds), and generation IDs from Probe messages.
System(su)->router#show ip dvmrp route
flag characters used:
-------------
V Neighbor is verified.
P Neighbor supports pruning.
G Neighbor supports generation ID.
N Neighbor supports netmask in prunes and grafts.
S Neighbor supports SNMP.
M Neighbor supports mtrace.
----------------
10.5.10.0/255.255.255.0 [3] Uptime: 61103 , expires: 0
via neighbor: 10.5.60.2 version: 3
Generation ID gen id: 1331801871
10.5.20.0/255.255.255.0 [2] Uptime: 61103 , expires: 0
via neighbor: 10.5.60.2 version: 3
Generation ID gen id: 1331801871
10.5.30.0/255.255.255.0 [2] Uptime: 61103 , expires: 0
via neighbor: 10.5.60.2 version: 3
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