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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02
Chapter 42 Configuring IP Multicast Routing
Configuring Advanced DVMRP Interoperability Features
Beginning in privileged EXEC mode, follow these steps to customize the summarization of DVMRP
routes if the default classful autosummarization does not suit your needs. This procedure is optional.
Note At least one more-specific route must be present in the unicast routing table before a configured
summary address is advertised.
To remove the summary address, use the no ip dvmrp summary-address address mask [metric value]
interface configuration command.
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 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 command.
Step 3
ip dvmrp summary-address address
mask [metric value]
Specify a DVMRP summary address.
• For summary-address address mask, specify the summary IP
address and mask that is advertised instead of the more specific
route.
• (Optional) For metric value, specify the metric that is advertised
with the summary address. The default is 1. The range is 1 to 32.
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.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Specify the interface connected to the DVMRP router, and enter
interface configuration mode.
Step 3
no ip dvmrp auto-summary Disable DVMRP autosummarization.
Step 4
end Return to privileged EXEC mode.