multicast¶

bridge config¶

There are bugs in kernel when forwarding non 224.0.0.* multicast traffic through bridges, so disable snooping:

host# echo 0 > /sys/devices/virtual/net/br0/bridge/multicast_snooping

http://troglobit.com/blog/2013/07/09/multicast-howto/

Then to make it persistent... /etc/sysconfig/network-scripts/ifup-post calls /sbin/ifup-local ${DEVICE} so add there

#!/bin/sh
#/sbin/ifup-local ${DEVICE}

if [[ "$1" == "br0" ]]
then
  if [[ -e "/sys/devices/virtual/net/$1/bridge/multicast_snooping" ]]
  then
    echo "Setting /sys/devices/virtual/net/$1/bridge/multicast_snooping."
    echo 0 > /sys/devices/virtual/net/$1/bridge/multicast_snooping
  else
    echo "Warning: can not find /sys/devices/virtual/net/$1/bridge/multicast_snooping"
  fi
#else
  #DO_NOTHING
fi

iptables¶

# multicast (igmp; Internet group management protocol)
iptables -I INPUT -p igmp -j ACCEPT

# Service config
iptables -I INPUT -m addrtype --dst-type MULTICAST -m state --state NEW -m multiport -p udp -s 10.20.0.0/16 --dports 5404,5405 -j ACCEPT

# iperf def port
iptables -I INPUT -m addrtype --dst-type MULTICAST -p udp --dport 5001 -j ACCEPT

test with iperf¶

Server:

# iperf -s -u -B 224.1.1.1 -i 1

Client:

# iperf -c 224.1.1.1 -u -T 32 -t 3

Problems: - Things to watch out for. Apparently iperf has issues if the ‘server’ is running on a computer with multiple interfaces. But aside from that, this worked. - Another thing to be careful of; the iperf test client will work correctly even if /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts is set (to 1). In this case, running iperf as a server and trying to ping the multicast address will NOT work. Whether this matters is dependent on your multicast needs.

netstat¶

Show joined groups:

# netstat -g
# cat /proc/net/igmp
# ip maddress list

tcpdump¶

Capture multicast traffic:

# tcpdump -n  -vv net 224.0.0.0/4

ping¶

# ping 224.1.1.1  Ping specific IP
# ping 224.0.0.1  All hosts configured for multicast will respond with their IP addresses