Linux – Enable multicast on dumthe interface on startup

centoslinuxlinux-networkingmulticastredhat

I have a dummy interface on a Centos 6.3 machine which I would like to use for multicast traffic. The problem is it does not come up with the MULTICAST option by default; I need to manually add it with ifconfig dummy0 multicast.

Is it possible to configure the interface to start with multicast enabled? I haven't been able to find any configuration options that do that, and experimenting with adding things like MULTICAST=yes to /etc/sysconfig/network-scripts/ifcfg-dummy0 have not been successful. Is there a configuration option I am missing, or am I going to need to put the ifconfig command in an init script?

Best Answer

Looking through /etc/sysconfig/network-functions, there is no "MULTICAST" option for the interface config scripts.

By default your interface SHOULD support multicast traffic. It may be that your network does not support multicast. Where I work, we have to enable multicast on our VLANs at the switch layer.

Related Solutions

Iptables – Unicast to multicast via iptables

Do you have ip forward enabled on kernel ?

# sysctl -a 2>&1 | grep ip_forward
net.ipv4.ip_forward=1

You need it to pass traffic from one interface to another (a.k.a. the FORWARD table rules).

Edit:

There is other sysctl setting, that I suspect that will be related:

net.ipv4.conf.all.mc_forwarding

and per interface, and for ipv6.

That "mc" really sounds to multicast, but I do not have kernel docs at hand to be 100% sure.

Try setting to 1, if doesn't work always you can return to the default 0.

Edit:

from networking/ip-sysctl.txt:

conf/all/mc_forwarding must also be set to TRUE to enable multicast routing

Centos – how to add iptables rules for two NICs on CentOS(act as a gateway)

A quick test:

Control Panel -> Windows Firewall (under System and Security, if you do that sort of thing). In the left pane, click 'Turn Windows Firewall On/Off', then turn off the Firewall in the right pane.

If you can ping it then, great... you can turn it back on, and allow ping by using the directions at http://www.sysprobs.com/enable-ping-reply-windows-7.

If that doesn't work, another quick test would be to shutdown iptables, just for troubleshooting purposes, of course. Even if you don't remember messing with it, it's worth testing...

sudo /etc/init.d/iptables stop

Best Answer

Related Solutions

Iptables – Unicast to multicast via iptables

Centos – how to add iptables rules for two NICs on CentOS(act as a gateway)

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