Very Basic Multitask and OSPF questions

Do routers by default listen and accept traffic from the Multicast ip address range 224.0.0.0 to 239.255.255.255 ?
Or do you have to be running a service on the router - such as OSPF for it to accept traffic from the multicast network range ?
For example in OSPF will all non DR routers accept traffic from 224.0.0.5 ?
What happens if a non DR router receives traffic directed to the DR ip address of 224.0.0.6 ? Does the router simply drop it ?

Many thanks in advance for any help on this.

I note from a reditt forum the following :
" If you enable ospf it will join to the 224.0.0.5 all ospf group. "

That kind off answers my question. Do you need a service that uses multicast to be running on your router for that router to accept multicast directed traffic ?

Hello Charles

Yes. This essentially answers your initial questions. In order for a router, or any network device for that matter, to “listen” to multicast addresses, it must be running a service that listens to such addresses. If OSPF is enabled on a router it will listen and communicate on 224.0.0.5. If it is a DR, it will listen to both 224.0.0.5 and 224.0.0. If it is participating in EIGRP, it will listen and communicate on 224.0.0.10. For RIP, 224.0.0.9.

Additionally, devices can join multicast address groups when using specific applications such as audio or video applications that support it. In this case, devices will use the Internet Group Management Protocol (IGMP) to join multicast groups for such purposes. Multicast is quite an extensive subject and you can find out more about it at this course page:


I hope this has been helpful!

Laz

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Thank you Laz for that explanation. Much appreciated.

Charlie

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