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Symptoms: Multicast Traffic Not Crossing Router

  • A multicast video streaming application works perfectly within the same VLAN.
  • Receivers on other VLANs/subnets do not receive any multicast traffic.
  • Unicast traffic between the VLANs works fine (routing is confirmed functional).
  • The multicast source is sending to group 239.1.1.1 on VLAN 10.
  • Receivers on VLANs 20 and 30 have joined group 239.1.1.1 but receive nothing.
  • Packet captures on the receiver VLAN show no multicast packets for 239.1.1.1.
  • The router connecting the VLANs shows no multicast routing entries for the group.
  • The issue has existed since the multicast application was first deployed across VLANs.