Setting Up Tunnels to Support Multicast Packets

Setting Up Tunnels to Support Multicast Packets

If your routers do not support multicast routing, you can support multicast packets by creating tunnels between the networks. Any Silicon Graphics workstation running IRIX Version 5.2 or later can be configured as the endpoint of a tunnel. With tunneling, the multicast packets are encapsulated inside unicast packets, and then are sent to the other end of the tunnel. They are converted back into multicast packets when they are received.

Figure 3-2 shows an example of a setup with a tunnel between networks A and C.

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Figure 3-2 : A Tunnel Between Networks A and C To create the tunnel, edit the file /etc/mrouted.conf. Step-by-step instructions follow:

Select the systems on each network that you will use for the sending and receiving end of the tunnel.
Choose a system that is running IRIX Version 5.2 or later, is fast, and is not used extensively. The audio and video data may be intermittent if the system you select is slow or overloaded.
If you haven't already done so, install the eoe2.sw.ipgate subsystem from your IRIX distribution source.
As root, edit the file /etc/mrouted.conf on the sending and receiving end of the tunnel. Note that these endpoints can be separated by many routers; you can use any machine on the network that is running IRIX Version 5.2 or later.
Add the following line for each network to which you want to establish a tunnel.

tunnel <local IP address> <remote IP address>
In the above example, the system on network D would have the following entry:

tunnel 192.26.58.1 192.48.170.2
The system on network A would have the following entry:

tunnel 192.48.170.2 192.26.58.1
You can specify other optional settings for the tunnel. For details, see the mrouted(1M) reference page.
Restart the system.

Note: One copy of the multicast packets is sent for each tunnel entry in mrouted.conf. This results in extra network traffic. For example, suppose you have a workstation with one network interface and you set up tunnels to workstations on three other networks. The packets are replicated three times.