Cisco 3750G - Catalyst Integrated Wireless LAN Controller, Руководство по настройке

Страница: 1018 / 1204

40-44
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 40 Configuring IP Multicast Routing
Configuring Advanced DVMRP Interoperability Features
Cisco devices do not perform DVMRP multicast routing among each other, but they can exchange
DVMRP routes. The DVMRP routes provide a multicast topology that might differ from the unicast
topology. This enables PIM to run over the multicast topology, thereby enabling sparse-mode PIM over
the MBONE topology.
When DVMRP unicast routing is enabled, the router or switch caches routes learned in DVMRP report
messages in a DVMRP routing table. When PIM is running, these routes might be preferred over routes
in the unicast routing table, enabling PIM to run on the MBONE topology when it is different from the
unicast topology.
DVMRP unicast routing can run on all interfaces. For DVMRP tunnels, it uses DVMRP multicast
routing. This feature does not enable DVMRP multicast routing among Cisco routers and multilayer
switches. However, if there is a DVMRP-capable multicast router, the Cisco device can do PIM/DVMRP
multicast routing.
Beginning in privileged EXEC mode, follow these steps to enable DVMRP unicast routing. This
procedure is optional.
To disable this feature, use the no ip dvmrp unicast-routing interface configuration command.
Rejecting a DVMRP Nonpruning Neighbor
By default, Cisco devices accept all DVMRP neighbors as peers, regardless of their DVMRP capability.
However, some non-Cisco devices run old versions of DVMRP that cannot prune, so they continuously
receive forwarded packets, wasting bandwidth.
Figure 40-6 shows this scenario.
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2
interface interface-id Specify the interface that is connected to the DVMRP router, and enter
interface configuration mode.
Step 3 ip dvmrp unicast-routing Enable DVMRP unicast routing (to send and receive DVMRP routes).
This feature is disabled by default.
Step 4
end Return to privileged EXEC mode.
Step 5 show running-config Verify your entries.
Step 6 copy running-config startup-config (Optional) Save your entries in the configuration file.