3

Environment: Two servers connected through a router, both running Ubuntu 16.04

I use the following commands to disable multicast:

ifconfig eno1 -multicast

or

ip link set eno1 multicast off

And check the result, no multicast flag:

$ ifconfig eno1
eno1      Link encap:Ethernet  HWaddr f8:ca:b8:4b:5b:88  
          inet addr:192.168.1.240  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::34c4:560f:208a:9249/64 Scope:Link
          UP BROADCAST RUNNING  MTU:1500  Metric:1
          RX packets:193 errors:0 dropped:0 overruns:0 frame:0
          TX packets:742 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:39493 (39.4 KB)  TX bytes:602751 (602.7 KB)
          Interrupt:20 Memory:f7200000-f7220000

Then I use iperf to test multicast, One server sends packages:

$ iperf -c 226.94.1.1 -u -i 1

Another server still receives packages:

$ iperf -s -u -B 226.94.1.1 -i 1

------------------------------------------------------------
Server listening on UDP port 5001
Binding to local address 226.94.1.1
Joining multicast group  226.94.1.1
Receiving 1470 byte datagrams
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  3] local 226.94.1.1 port 5001 connected with 192.168.1.240 port 36855
[ ID] Interval       Transfer     Bandwidth        Jitter   Lost/Total Datagrams
[  3]  0.0- 1.0 sec   128 KBytes  1.05 Mbits/sec   0.002 ms    0/   89 (0%)
[  3]  1.0- 2.0 sec   128 KBytes  1.05 Mbits/sec   0.002 ms    0/   89 (0%)

It seems multicast mode not disabled. I don't know why.
Thanks for any help.

2
  • If you check the state of the interface while iperf is running, does it still show multicast disabled?
    – Andy Dalton
    Feb 12, 2017 at 3:07
  • Yes, multicast flag not showed from the result of "ifconfig" when running iperf.
    – fillzero
    Feb 12, 2017 at 3:24

1 Answer 1

Reset to default
2

Try removing multicast manually from the avahi-daemon config:

Edit /etc/init/avahi-daemon.conf

Replace the line start on (filesystem and started dbus) with start on (never and filesystem and started dbus)

Then replace the stop line with stop on stopping dbus

If the stop line doesn't exist, just add stop on stopping dbus below the start on line

You can try restarting networking after for the changes to take effect, or just do a reboot which should do the trick.

1
  • 2
    I changed the /etc/init/avahi-daemon.conf and reboot, but multicast still works.
    – fillzero
    Mar 2, 2017 at 10:43

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