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Configuring Advanced DVMRP Interoperability Features
Disabling DVMRP Autosummarization
By default, the software automatically performs some level of DVMRP summarization. Disable this
function if you want to advertise all routes, not just a summary. In some special cases, you can use the
neighboring DVMRP router with all subnet information to better control the flow of multicast traffic in
the DVMRP network. One such case might occur if the PIM network is connected to the DVMRP cloud
at several points and more specific (unsummarized) routes are being injected into the DVMRP network
to advertise better paths to individual subnets inside the PIM cloud.
If you configure the ip dvmrp summary-address interface configuration command and did not
configure no ip dvmrp auto-summary, you get both custom and autosummaries.
Beginning in privileged EXEC mode, follow these steps to disable DVMRP autosummarization. This
procedure is optional.
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
no ip dvmrp auto-summary
Step 4
end
Step 5
show running-config
Step 6
copy running-config startup-config
To re-enable auto summarization, use the ip dvmrp auto-summary interface configuration command.
Adding a Metric Offset to the DVMRP Route
By default, the switch increments by one the metric (hop count) of a DVMRP route advertised in
incoming DVMRP reports. You can change the metric if you want to favor or not favor a certain route.
For example, a route is learned by multilayer switch A, and the same route is learned by multilayer
switch B with a higher metric. If you want to use the path through switch B because it is a faster path,
you can apply a metric offset to the route learned by switch A to make it larger than the metric learned
by switch B, and you can choose the path through switch B.
Beginning in privileged EXEC mode, follow these steps to change the default metric. This procedure is
optional.
Command
Step 1
configure terminal
Step 2
interface interface-id
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
44-60
Purpose
Enter global configuration mode.
Specify the interface connected to the DVMRP router, and enter
interface configuration mode.
Disable DVMRP autosummarization.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Purpose
Enter global configuration mode.
Specify the interface to be configured, and enter interface configuration
mode.
Chapter 44
Configuring IP Multicast Routing
OL-12247-04
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