DVMRP Tunnelling

Unanswered Question
Mar 24th, 2009

I have to get some multicast traffic across a non multicast network, and have had a suggestion I use DVMRP tunnels. The site routers are 3750, so no GRE,.

Try as I might, I don't seem to get it working - I don't think the tunnel it establishing properly , a sh int shows nothing in or out. A debug ip pack with an access list to the tunnel destination shows nothing.

sh int tu0

Tunnel0 is up, line protocol is up

Hardware is Tunnel

Interface is unnumbered. Using address of Vlan512 (

MTU 9112 bytes, BW 100 Kbit, DLY 50000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation TUNNEL, loopback not set

Keepalive not set

Tunnel source (Loopback0), destination

Tunnel protocol/transport IP/IP (DVMRP)

Tunnel TTL 255, Fast tunneling enabled

Tunnel transport MTU 1480 bytes

Last input never, output never, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/0 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts (0 IP multicasts)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

0 packets output, 0 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

IOS is 12.2(50)se.

Any suggestions about what I have wrong?

I have this problem too.
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ldardon Mon, 03/30/2009 - 12:17

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.

paul.matthews Tue, 03/31/2009 - 01:53

Thanks for the confirmation - I had kind of come to the conclusion that to do the tunnel, it would need to be a real DVMRP tunnel at the other end.


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