Configuring DVMRP
Configuring DVMRP
page 5-16
OmniSwitch AOS Release 7 Advanced Routing Configuration Guide
March 2011
Grafting
A pruned branch will be automatically reattached to the multicast delivery tree when the prune times out.
However, the graft mechanism provides a quicker method to reattach a pruned branch than waiting for the
prune to time out. As traffic is forwarded, routers that do not want multicast traffic send Prune messages to
signal the upstream router to stop sending the traffic. If new IGMP membership requests are later received
by the downstream router, the router can send Graft messages to the upstream router and wait for acknowl-
edgment (a Graft Ack).
The
ip dvmrp graft-timeout
command enables you to set the Graft message retransmission value. This
value defines the duration of time that the router will wait before retransmitting a Graft message if it has
not received a Graft-Ack message acknowledging that a previously transmitted Graft message was
received. For example, enter the following to set the Graft message retransmission value to 5 seconds:
-> ip dvmrp graft-timeout 5
Note.
Current global DVMRP parameter values, including the
ip dvmrp graft-timeout
value, can be
viewed via the
show ip dvmrp
command.
Tunnels
DVMRP networks may use DVMRP tunnels to interconnect two multicast-enabled networks across non-
multicast networks. In a DVMRP tunnel, IP multicast packets are encapsulated in unicast IP packets so
that the multicast traffic can traverse a non-multicast network.
The
ip interface tunnel
command enables you to add or delete an IP-IP tunnel and DVMRP can then be
run over this tunnel. Any packets sent through the tunnel will be encapsulated in an outer IP header. For
example, the following command would create a tunnel between local address 23.23.23.1 and remote
address 155.2.2.2:
-> ip interface “tnl-1” tunnel source 23.23.23.1 destination 155.2.2.2
The local tunnel address must match an existing IP interface on a router that has been configured for
DVMRP. The tunnel’s remote address must be the IP address of the remote DVMRP router to which the
tunnel is connected.
Important.
DVMRP needs to be enabled on the IP interface of the source address of the tunnel and also
on the configured tunnel interface.The tunnel will be operational only when the DVMRP interface is also
operational. To enable DVMRP on an interface, use the
ip dvmrp interface
command. For more informa-
tion, refer to
“Enabling DVMRP on a Specific Interface” on page 5-10
.
Note
.
Current DVMRP tunnels, including the tunnels’ operational (OPER) status and TTL values, can be
viewed via the
show ip dvmrp tunnel
command. The status of the DVMRP interface can be viewed via
the
show ip dvmrp interface
command.