To access multicast service on a Linux host requires configuring at least one network interface, configuring a default route for the host, and configuring a route for class D (224.0.0.0/8) traffic). The msend and mreceive utilities can be used to send and receive multicast traffic for diagnostic purposes.
Configuring multicast on a Linux host
To access multicast services on a Linux host requires configuring a network interface, a default route for the host, and a route for class D traffic. Following is an example:
ifconfig eth0 10.10.10.10/24
route add default gw 10.10.10.20
route add -net 224.0.0.0/8 dev eth0
msend and mreceive
The msend and mreceive utilities can be used to send and receive multicast traffic for diagnostic purposes. Following are examples of their use (see "man msend" and "man mreceive" for more details):
PC1% msend -g 224.2.2.2 -p 2222 -t 8 -text "PC1"
PC1% mreceive -g 224.3.3.3 -p 3333
PC2% msend -g 224.3.3.3 -p 3333 -t 8 -text "PC2"
PC2% msend -g 224.1.1.1 -p 1111 -t 8 -text "PC2"
PC3% msend -g 224.2.2.2 -p 2222 -t 8 -text "PC3"
PC3% msend -g 224.3.3.3 -p 3333 -t 8 -text "PC3"
PC4% mreceive -g 224.1.1.1 -p 1111
PC4% mreceive -g 224.2.2.2 -p 2222
PC4% mreceive -g 224.3.3.3 -p 3333
Commands to query IP multicast group membership
WARNING: using ping to multicast groups seems to kill multicast forwarding in GNS3!
The ping command can be used to query a subnet for IP multicast group membership:
PC1% msend -g 224.3.3.3 -p 3333 -join
PC2% msend -g 224.3.3.3 -p 3333 -join
PC2% mreceive -g 224.3.3.3 -p 3333
PC3% ping 224.3.3.3
