Linux 7 Multicast Configuration

Internal

• Linux 7 Network Configuration

Concepts

Multicast

Procedure

Multicast at Kernel Level

Make sure multicast is enabled at kernel level.

To compile multicast support into the kernel, CONFIG_IP_MULTICAST must be present in the kernel configuration file. The kernels are usually compiled with multicast support. If netstat -ng shows multicast groups being registered to, it means multicast support is available in kernel. For more details, see Troubleshooting below.

Multicast Support at Interface Level

• Verify that the network interface you plan to use for multicast traffic has multicast enabled, and if not, turn it on.
• Configure multicast routing: Configure Multicast Routing
• If iptables runs on the system, allow multicast traffic for the interface that will handle multicast traffic: Configure iptables to allow Multicast
• Test it. For more details see the Troubleshooting section.

/proc

/proc/net/dev_mcast

Contains Layer2 multicast groups which a device is listening to (interface index, label, number of references, number of bound addresses).

/proc/net/igmp

Contains IPv4 multicast groups joined by this host.

/proc/net/igmp6

Contains IPv6 multicast groups joined by this host.

Troubleshooting

Display Multicast Group Membership Information

netstat -g

displays multicast group membership information for IPv4 and IPv6. Optionally use -n to prevent DNS lookups (faster).

The same information can be obtained from /proc:

cat /proc/net/dev_mcast
cat /proc/net/igmp
cat /proc/net/igmp6

For more details on these files see /proc above.

ip has multicast querying abilities. See:

ip Multicast Support

Send Multicast Traffic

See

Java Network Traffic Generator

Organizatorium

TODO http://lartc.org/howto/lartc.multicast.html

echo 1 > /proc/sys/net/ipv4/ip_forward