05-09-2008 02:18 PM - edited 03-03-2019 09:53 PM
I am having difficulty understanding what the difference is between these 2 commands. All the docs that I read say that they both allow the router to forward multicast packets but the "join-group" command will actually cause the router to accept the packets. Can anyone help me understand what is meant exactly by "accept" the packets?
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05-09-2008 10:30 PM
harold,
I just need to clarify something.
when igmp-join is used, would this be more cpu taxing if testing high volume of multicast. and in which case, should be used with caution.
TIA
Sam
05-09-2008 05:44 PM
Izack,
"ip igmp static-group" configures a static connected member for a specific group. Traffic to that group will be fast-switched to the interface where this comamnd is configured rather than process switched. This command is usually used to forward mcast traffic down an interface.
"ip igmp join-group" causes the router to send an IGMP membership report on the interface where it is configured. The mcast packets will therefore be received and process switched by the router. This command is usually used for test purposes.
Regards,
05-09-2008 10:30 PM
harold,
I just need to clarify something.
when igmp-join is used, would this be more cpu taxing if testing high volume of multicast. and in which case, should be used with caution.
TIA
Sam
05-11-2008 04:39 AM
Sam,
Good point. I certainly wouldn't recommend using that command to enable a receiver for a multicast group with high bandwidth stream.
Regards,
05-10-2008 05:16 AM
Thank you for your response, that helps out a lot. I am still a little confused why a router would process a multicast packet? You mentioned it is for testing but is that the sole purpose of the command join-group? When the router processes the multicast packet what is really happening?
05-10-2008 06:52 AM
Izack,
It could be as simple as pinging a multicast group from a given source and the router on which the "ip igmp join-group" is configured for that same group will respond to that ping. I often seen that as an easy way to test a new multicast network.
05-10-2008 07:52 PM
Thanks again Harold. The join-group sounds to me like a command reserved mostly for a lab environment. It sounds like there isn't much practical use for it besides simulating a multicast source.
05-11-2008 04:36 AM
Izack,
In your last statement you say simulating multicast source but this command rather simulate a multicast receiver.
I would tend to disagree with you last statement. Although I agree that one wouldn't use this command to perform capacity testing, I have used it many times in the past to perform functional tests and troubleshoot new multicast networks and it has helped me tremendously as it creates receivers without having to involved any workstations and requires very little configuration.
Regards,
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