Chapter 42 Configuring IP Multicast Routing

Configuring Basic DVMRP Interoperability Features

Configuring a DVMRP Tunnel

The software supports DVMRP tunnels to the MBONE. You can configure a DVMRP tunnel on a router or multilayer switch if the other end is running DVMRP. The software then sends and receives multicast packets through the tunnel. This strategy enables a PIM domain to connect to the DVMRP router when all routers on the path do not support multicast routing. You cannot configure a DVMRP tunnel between two routers.

When a Cisco router or multilayer switch runs DVMRP through a tunnel, it advertises sources in DVMRP report messages, much as it does on real networks. The software also caches DVMRP report messages it receives and uses them in its RPF calculation. This behavior enables the software to forward multicast packets received through the tunnel.

When you configure a DVMRP tunnel, you should assign an IP address to a tunnel in these cases:

To send IP packets through the tunnel

To configure the software to perform DVMRP summarization

The software does not advertise subnets through the tunnel if the tunnel has a different network number from the subnet. In this case, the software advertises only the network number through the tunnel.

Beginning in privileged EXEC mode, follow these steps to configure a DVMRP tunnel. This procedure is optional.

 

 

Command

Purpose

 

 

Step 1

 

 

 

 

configure terminal

Enter global configuration mode.

 

 

Step 2

 

 

 

 

access-listaccess-list-number {deny

Create a standard access list, repeating the command as many times as

 

 

 

permit} source [source-wildcard]

necessary.

 

 

 

 

For access-list-number, the range is 1 to 99.

 

 

 

 

The deny keyword denies access if the conditions are matched. The

 

 

 

 

permit keyword permits access if the conditions are matched.

 

 

 

 

For source, enter the number of the network or host from which the

 

 

 

 

packet is being sent.

 

 

 

 

(Optional) For source-wildcard, enter the wildcard bits in dotted

 

 

 

 

decimal notation to be applied to the source. Place ones in the bit

 

 

 

 

positions that you want to ignore.

 

 

 

 

Recall that the access list is always terminated by an implicit deny

 

 

 

 

statement for everything.

 

 

Step 3

 

 

 

 

interface tunnel number

Specify a tunnel interface, and enter interface configuration mode.

 

 

Step 4

 

 

 

 

tunnel source ip-address

Specify the source address of the tunnel interface. Enter the IP address

 

 

 

 

of the interface on the switch.

 

 

Step 5

 

 

 

 

tunnel destination ip-address

Specify the destination address of the tunnel interface. Enter the IP

 

 

 

 

address of the mrouted router.

 

 

Step 6

 

 

 

 

tunnel mode dvmrp

Configure the encapsulation mode for the tunnel to DVMRP.

 

 

Step 7

 

 

 

 

ip address address mask

Assign an IP address to the interface.

 

 

 

or

or

 

 

 

ip unnumbered type number

Configure the interface as unnumbered.

 

 

Step 8

 

 

 

 

ip pim [dense-mode sparse-mode]

Configure the PIM mode on the interface.

 

 

 

 

 

 

 

 

 

 

 

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OL-9775-02

 

 

42-41

 

 

 

 

 

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Cisco Systems 3750E manual Configuring a Dvmrp Tunnel, 42-41