How to ping to a multicast address for testing?

Environment

• Red Hat Enterprise Linux 5
• Red Hat Enterprise Linux 6
• Red Hat Enterprise Linux 7

Issue

• How to ping to a multicast address for testing?

Resolution

Red Hat Enterprise Linux 5

1. Run the following to ignore icmp broadcasts :

    # echo "0" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
   

2. Check the multicast addresses subscribed to :

    # ip maddr
   

3. Run ping with the multicast address :

    # ping -L  239.192.104.2
   
    # ping -L  224.0.0.1
   

Red Hat Enterprise Linux 6

• Red Hat Enterprise Linux 6 provides the omping package, which can be used to test multicast communication :
• When using omping specify the cluster ports in the command with -p. The default port of omping is UDP 4321. If this is not allowed in the iptables omping output will not show the multicast reply in the output.

SYNTAX

# omping <remote ip> <own ip>

# omping -p 5404 192.168.122.81 192.168.122.82
192.168.122.82 : waiting for response msg
192.168.122.82 : joined (S,G) = (*, 232.43.211.234), pinging
192.168.122.82 :   unicast, seq=1, size=69 bytes, dist=0, time=0.330ms
192.168.122.82 : multicast, seq=1, size=69 bytes, dist=0, time=0.438ms
192.168.122.82 :   unicast, seq=2, size=69 bytes, dist=0, time=0.609ms
192.168.122.82 : multicast, seq=2, size=69 bytes, dist=0, time=1.211ms
192.168.122.82 :   unicast, seq=3, size=69 bytes, dist=0, time=0.710ms
192.168.122.82 : multicast, seq=3, size=69 bytes, dist=0, time=1.060ms

Note : The omping package is only available via the RHEL High Availability Add-on.

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