Troubleshooting

Efficient Video Distribution Networks with.Multicast: IGMP Querier and PIM-DM
11
Troubleshooting Tips
If you are receiving video at the clients but no ports are showing up under 0.0.1 from the show ip igmp
snooping groups command, then Multicast is not working. They are receiving video because the traffic
is still being broadcasted to all ports (this is the default behavior of the switches). Recheck settings on
all switches.
If VLC on the client is stopped (you must press the Stop button to leave the multicast group), but
Wireshark is showing UDP traffic from 239.0.0.1, then the video is being broadcasted to all ports and
Multicast is not working. Check settings on all switches. Keep in mind that when the VLC client sends
a “leave group” message, that it takes a few seconds before the UDP frames stop.
Each time you want to leave the multicast group, be sure to do so by pressing the Stop button at the
bottom of the VLC media player or by closing the window using the X button. Pressing pause within the
player will not leave the group.
If the UDP frames are not making it to the receiver port and no video is seen at the receiver, the time
to live (TTL) value may need to be increased when starting the stream from the server. To do this, in
step 12 above, instead of clicking Stream, click Next, and set the TTL to 16. Then click Stream to
continue. This is only necessary on a routed network and does not apply to a “layer 2 only” network.
Some MP4 files will only display the first video frame locally on the VLC Video server, but are still being
streamed to the clients, which can be verified by the progress bar below the display. To get around
this issue, stream WMV/WMA or other files.
If you see traffic flooding on all ports of VLAN 10, make sure the snooping switch has learned an
mrouter port by using the command show ip igmp snooping mrouter.