Operation Manual

SFX SERIES USER’S GUIDE
Rev 2.2 50
Interface: sat0
Gateway: 0.0.0.0
Destination: 224.0.0.0
Netmask: 240.0.0.0
6. Local Application Rule 2
: Suppose that multicast packets with a destination of 224.1.1.1:1234 are being
received from eth0 and are being forwarded to eth1 via a multicast route. If there is no local application
running, the packets will be routed through the system as expected. Now suppose that an application that
listens to 224.1.1.1:1234 is started on the receiver (e.g. streaming video). As stated above, a static route is
required for this application to bind to the receiving socket. If this static route is:
Interface: eth0
Gateway: 0.0.0.0
Destination: 224.1.1.1
Netmask: 255.255.255.255
packets will be routed to both the application and eth1. However, if the static route is:
Interface: eth1
Gateway: 0.0.0.0
Destination: 224.1.1.1
Netmask: 255.255.255.255
then the packets will be routed to the application, but not to eth1. If you stop the application, 224.1.1.1
packets will be output on eth1. If you then restart the application, output of 224.1.1.1 packets on eth1 will
stop.
7. Local Application Rule 3
: Suppose that multicast packets with a destination of 224.1.1.1:1234 are being
received on eth0 and are being forwarded to all interfaces (eth0 and eth1) by a multicast route. Now
suppose that an application that listens to 224.1.1.1:1234 is started on the receiver. As stated above, a static
route is required for this application to bind to the receiving socket. If this static route is
:
Interface: eth0
Gateway: 0.0.0.0
Destination: 224.1.1.1
Netmask: 255.255.255.255
then the application will get two copies of each packet. This anomaly occurs because Linux forwards one
packet to the application immediately when it is received on the interface and another is received when the
kernel routing subsystem bounces a copy of the packet back to the interface for transmission.
8. Local Application Rule 4
: Suppose that multicast packets with a destination of 224.1.1.1:1234 are being
received on sat0 and are being forwarded to all interfaces (eth0 and eth1) by a multicast route. Now suppose
that an application that listens to 224.1.1.1:1234 is started on the receiver. A static route for this application is
entered, to bind to the receiving socket:
Interface: eth0
Gateway: 0.0.0.0
Destination: 224.1.1.1
Netmask: 255.255.255.255
From the previous Local Application Rule #2, we know that output of 224.1.1.1 on eth0 will stop. The output
of 224.1.1.1 on eth1 will, however, continue. Only if the incoming multicast IP packets are fragmented, the
application may see occasional packet loss. The loss will not be constant or periodic and no packets will be