rafaeltuelho/linux-mcast-net.md

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Linux Multicasting Network troubleshooting...

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linux-mcast-net.md

to see mcast group information

ip maddr show

to see if mcast is enabled on your current kernel

grep "MULTICAT" /usr/src/kernels/<kernael version>.x86_64/.config
CONFIG_IP_MULTICAST=y

Display multicast group membership information

netstat -g
IPv6/IPv4 Group Memberships
Interface       RefCnt Group
--------------- ------ ---------------------
lo              1      all-systems.mcast.net
enp0s25         2      239.255.2.3
enp0s25         1      all-systems.mcast.net
enp0s25         3      224.0.0.251
virbr4          1      224.0.0.251
...

to see if mcast is enabled on a given ifc

ip a s <ifc name>
ip a s eth0
# you should see <...,MULTICAST,...>...

# to enable mcast
sudo ifconfig <ifc name> multicast

# to disable mcast
sudo ifconfig <ifc name> -multicast

to enable mcast on RHEL 7 Firewalld

sudo firewall-cmd --permanent --runtime --add-rule ipv4 filter INPUT 0 -m pkttype --pkt-type multicast -j ACCEPT 
sudo firewall-cmd --permanent --runtime --add-rule ipv6 filter INPUT 0 -m pkttype --pkt-type multicast -j ACCEPT
sudo firewall-cmd --direct --get-all-rules
sudo firewall-cmd --reload

Additional references

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