====== Show Connected Multicasts ======
Jun 2017
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This page discusses two tools. ngstat and ip
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To show if an interface is actively listening to any multicast streams, we can show this by using the netstat command: (netstat -ng)
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netstat -ng
IPv6/IPv4 Group Memberships
Interface RefCnt Group
--------------- ------ ---------------------
lo 1 224.0.0.1
eth2 4 239.0.200.1
eth2 1 224.0.0.1
eth3 1 224.0.0.1
eth4 1 224.0.0.1
eth5 1 224.0.0.1
eth0 1 224.0.0.1
eth1 1 224.0.0.1
lo 1 ff02::1
eth2 1 ff02::1
eth3 1 ff02::1
eth4 1 ff02::1
eth5 1 ff02::1
eth0 1 ff02::1
eth1 1 ff02::1
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This is a packager (v8) that I have setup a service on. That service is an ABR service containing four streams, so the line:
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eth2 4 239.0.200.1
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Is interesting to me, I can see that from address 239.0.200.1 (the MFEL multicast output) Interface 2 is connected to four multicasts.
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Another tool we can use is ip maddr this gives more information.
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1: lo
inet 224.0.0.1
inet6 ff02::1
2: eth2
link 01:00:5e:00:c8:01
link 33:33:00:00:00:01
link 01:00:5e:00:00:01
inet 239.0.200.1 users 4
inet 224.0.0.1
inet6 ff02::1
3: eth3
link 01:00:5e:00:00:01
inet 224.0.0.1
inet6 ff02::1
4: eth4
link 33:33:00:00:00:01
link 01:00:5e:00:00:01
inet 224.0.0.1
inet6 ff02::1
5: eth5
link 01:00:5e:00:00:01
inet 224.0.0.1
inet6 ff02::1
6: eth0
link 33:33:00:00:00:01
link 01:00:5e:00:00:01
inet 224.0.0.1
inet6 ff02::1
7: eth1
link 01:00:5e:00:00:01
inet 224.0.0.1
inet6 ff02::1
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On interface 2, we can see the same information, but just formatted in a different way:
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eth2\\
link 01:00:5e:00:c8:01\\
link 33:33:00:00:00:01\\
link 01:00:5e:00:00:01\\
inet 239.0.200.1 users 4\\
inet 224.0.0.1\\
inet6 ff02::1\\
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