Multicast is when someone sends a single set of data packets across a network to multiple selected users at the same time. Multicast is subscription-based: Computers that want to receive multicast traffic use ICMP messages to let routers know which multicast addresses they want to subscribe to. The routers are then able to calculate which multicast messages they need to send to receivers on their different interfaces. A packet is considered a multicast packet if the destination IP address is in the range 224.0.0.0 to 239.255.255.255.

The Multicast Activity overview (ANALYZE > Overview > IP Traffic > Multicast Activity) lets you view multicast activity in a list format.

1. If you want to limit your results to a particular type of multicast traffic, select required multicast group. Otherwise select All Multicast.

   Multicast groups help you filter your data if you are only interested in a particular type of multicast traffic. PerformanceGuard comes with preconfigured groups for common types of multicast traffic, LLMNR and SSDP, and PerformanceGuard administrators can set up additional groups. See also Manage Multicast Groups.

2. Select required direction:
   • Sent: Outgoing multicast traffic measured on servers that send multicast traffic.
     
     In the example illustration (click thumbnail to view image in full size) sent multicast traffic is measured on the computer with the green dot:
     
   • Received: Incoming multicast traffic measured computers that receive such data.
     
     In the example illustration (click thumbnail to view image in full size) received multicast traffic is measured on the computers with the green dots:
     
     
     
3. If required, you can limit your overview to a particular group of computers with the Agent menu:
   
   • If you selected Sent in the previous step, use the menu to limit your overview to multicast traffic sent from a particular location/network
   • If you selected Received in the previous step, use the menu to limit your overview to multicast traffic received at a particular location/network 
     
     If you don't want to limit your overview this way, select All agents.
     
     
4. Select the required Interval (that is the period of time that you want to cover). If the predefined intervals don't suit you, select Custom to specify your own interval.

5. If required, you can enter all or part of a server IP address to limit the search to multicast servers with that IP address.

   Examples: To limit your search to a server with the IP address 192.168.40.72, specify that IP address. To limit your search to servers with an IP address that begins with 192.168.40, specify those IP address segments in the first three fields, and leave the last field blank.

6. Click the Update button.

   It may take some time to generate the list, especially if you have selected all multicast groups and all computers.