Cisco Systems 78-11741-02 manual Configuring a Dvmrp Tunnel, IPC-539

Configuring DVMRP Interoperability

Basic DVMRP Interoperability Configuration Task List

171.69.214.203 -> 0.0.0.0 [1/0/pim/querier/down/leaf] 171.69.214.18 -> 171.69.214.20 (mm1-45e.cisco.com) [1/0/pim] 171.69.214.18 -> 171.69.214.19 (mm1-45c.cisco.com) [1/0/pim] 171.69.214.18 -> 171.69.214.17 (mm1-45a.cisco.com) [1/0/pim]

See the “DVMRP Interoperability Example” section later in this chapter for an example of how to configure a PIM router to interoperate with a DVMRP router.

Configuring a DVMRP Tunnel

The Cisco IOS software supports DVMRP tunnels to the MBONE. You can configure a DVMRP tunnel on a router if the other end is running DVMRP. The software then sends and receives multicast packets over the tunnel. This strategy allows a PIM domain to connect to the DVMRP router in the case where all routers on the path do not support multicast routing. You cannot configure a DVMRP tunnel between two routers.

When a Cisco router runs DVMRP over a tunnel, it advertises sources in DVMRP report messages much as it does on real networks. In addition, the software caches DVMRP report messages it receives and uses them in its Reverse Path Forwarding (RPF) calculation. This behavior allows the software to forward multicast packets received over the tunnel.

When you configure a DVMRP tunnel, you should assign a tunnel an address in the following two cases:

•To enable the sending of IP packets over the tunnel

•To indicate whether the Cisco IOS software should perform DVMRP summarization

You can assign an IP address either by using the ip address interface configuration command, or by using the ip unnumbered interface configuration command to configure the tunnel to be unnumbered. Either of these two methods allows IP multicast packets to flow over the tunnel. The software will not advertise subnets over the tunnel if the tunnel has a different network number from the subnet. In this case, the software advertises only the network number over the tunnel.

To configure a DVMRP tunnel, use the following commands in interface configuration mode:

	Command	Purpose
Step 1
	Router(config-if)# interface tunnel number	Specifies a tunnel interface in global configuration mode
		and puts the router into interface configuration mode.
Step 2
	Router(config-if)# tunnel source ip-address	Sets the source address of the tunnel interface. This address
		is the IP address of the interface on the router.
Step 3
	Router(config-if)# tunnel destination	Sets the destination adddress of the tunnel interface. This
	ip-address	address is the IP address of the mrouted multitask router.
Step 4
	Router(config-if)# tunnel mode dvmrp	Configures a DVMRP tunnel.
Step 5
	Router(config-if)# ip address address mask	Assigns an IP address to the interface.
	or	or
	Router(config-if)# ip unnumbered type number	Configures the interface as unnumbered.
Step 6
	Router(config-if)# ip pim [dense-mode	Configures PIM on the interface.
	sparse-mode]
Step 7
	Router(config-if)#ip dvmrp accept-filter	Configures an acceptance filter for incoming DVMRP
	access-list [distance ip neighbor-list	reports.
	access-list]

Cisco IOS IP Configuration Guide

IPC-539