Multicast Deployment - Instructions for Testing

STEP 1: Enable Multicast Routing

Routers in the core of the LEARN network and the access routers at the sites listed in the LEARN multicast deployment page have been configured to support multicasting.

The hosts on the IP subnet directly connected to the LEARN router can therefore participate in multicasting. But you will first need to enable IGMP snooping on ALL layer 2 devices between the LEARN access router and the hosts on which you wish to run multicast applications.

STEP 2: Enable IGMP Snooping in your network

As indicated above, you need to enable IGMP snooping on ALL layer 2 devices between the LEARN access router and the host on which you wish to run multicast applications. Consider the following scenario:

In this network, although the host and the inside interface of the access router are on the same IP subnet, they are connected via two Layer 2 switches A and B. So, in this case, it is necessary to enable IGMP snooping on both A and B.

Some layer 2 switches require that IGMP snooping be enabled on a per-VLAN basis. If this is the case, and the above IP subnet corresponds to VLAN number X, it is required to enable IGMP snooping in VLAN X on both switches A and B.

Please refer to the user manual(s) of your layer 2 switch(es) for exact information on enabling IGMP snooping.

STEP 3: Test Multicast Routing

You can test the routing of multicast packets from/to your host by running the asmping application as follows.

  1. Download the asmping application from the ssmping home page. You can download the binary or compile from source. The windows binary of asmping is also available.
  2. Run the asmping application as indicated below, to test multicast connectivity to the LEARN server on multicast group
    asmping -4

    You should see an output like the following:

    asmping joined (S,G) = (*,
    pinging from
      unicast from, seq=1 dist=3 time=6.449 ms
      unicast from, seq=2 dist=3 time=6.525 ms
    multicast from, seq=2 dist=2 time=6.928 ms
    multicast from, seq=3 dist=2 time=6.653 ms
      unicast from, seq=3 dist=3 time=6.727 ms
    multicast from, seq=4 dist=2 time=4.361 ms
      unicast from, seq=4 dist=3 time=6.505 ms
    multicast from, seq=5 dist=2 time=4.303 ms
      unicast from, seq=5 dist=3 time=6.391 ms

If multicast routing is working, you should get multicast responses from the server. If you only get unicast responses, IGMP snooping in your Layer 2 equipment may not be working.

STEP 4: Test ability to receive a multicast stream

A number of video streams are being multicast for testing purposes. Follow the steps below to test whether you can receive the streams.

  1. Download the VideoLAN client. There are binaries available for Windows as well.
  2. Test whether you can receive the multicast stream on using the following command:
    vlc udp://@

    On Windows, run the VideoLAN client VLC, select File ---> Open Network Stream, and then select UDP/RTP Multicast and specify the address (or the corresponding multicast address for other streams).

STEP 5: Transmit a multicast stream

The same VideoLAN Client can be used to transmit a multicast video stream. See the VLC Streaming HowTo in VLC Documentation for more information.

If you wish to transmit a multicast stream, please contact the LEARN NOC to obtain an multicast IP address for transmission.


If you need any technical assistance in this regard, please contact us at noc AT learn DOT ac DOT lk