Troubleshooting multicast tunnels

OK, so you've set up a multicast tunnel, at both the multikit and liveGate ends, but multikit is not receiving any data. (For instance, you're not seeing anything being announced into the "Public Grab Bag" or "SDP default directory".) What's the problem?

There are two main possibilities:

  1. The machine on which you're running liveGate is not on the Multicast Internet after all.
  2. One or both of your tunnel endpoints is incorrect. (Each tunnel endpoint must denote the source address for packets from that endpoint.)
Re. 1: If you're unsure as to whether your liveGate host is really on the Multicast Internet, you can let us know its address (or name) and we can check it for you.

Re. 2: Unfortunately it's easy to set up the wrong tunnel endpoints, especially if one or both of the endpoint machines has more than one IP address.

First, when you run liveGate, do you see any "received packet from bad source" messages? If so, this indicates that you've specified the wrong endpoint address in your "liveGateInit" file. The endpoint address must be the source address of packets that arrive from your multikit machine. (Note that some users with PPP connections to the Internet actually have two IP addresses; if so, you need to make sure you specify the correct one.)

Otherwise, restart liveGate with debugging printout turned on: 

liveGate -d 2

If your tunnel from multikit is running correctly, you will see (at the liveGate end) several messages of the form: 

Groupsock...: created
UDPtunnel...: joined group ...

If you don't see any such messages, then this suggests that you've entered the wrong address (or name) as your tunnel endpoint in multikit. Make sure that the address/name that you've entered really is that of the liveGate machine.

If you do see messages like this, but multikit is still not receiving any announcements from the outside world, then you may have specified a tunnel endpoint in multikit that's an address for the liveGate machine, but not the source address of packets that are sent from that machine. (If multikit was run from a console or shell window, then you may see "received packet from bad source" error messages.) Note that liveGate outputs (to the console) its IP address as it starts up. This is likely to be the IP address that you should use in your multikit tunnel.

If you're still having problems, please let us know, and we'll try to help. Fortunately, tunnel configuration should become less of a "black art" in future versions of multikit/liveGate.

It's also possible to set up a multicast tunnel between two copies of multikit, rather than between multikit and liveGate. If you're having difficulties setting up a multikit<->multikit tunnel, then first check that the "tunnel locally only" checkbox (in the "Set up an MBone tunnel" menu) is turned off in the multikit that's already on the Multicast Internet.

If you're still having difficulties with a multikit<->multikit tunnel, then you may find it helpful to first try to set up a working multikit<->liveGate or liveGate<->multikit tunnel, using the tips mentioned above. Once you have this tunnel working, you should be able to replace the liveGate end with multikit (with tunneling turned on, of course).

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