L3 switch multicast range

[mfouad.jahmi]

hi Cisco Pro's,

what if am assigning an IP address to a device let's say 10.10.10.10/24 and i want the multicast to be like this 10.10.10.11/24 ( note the increment by one of the multicast IP last octet when compare to its last octet of the unicast IP )

how am i suppose to configure that on the L3 switch ?

thanks

MJ

[John Blakley]

What are you trying to accomplish? Multicast is sourced by the address to a specific group of addresses - 224.0.0.0 - 239.255.255.255 (depending on your scope). Are you asking how you can make your source be seen as 10.10.10.11/24 instead of 10.10.10.10/24?

[mfouad.jahmi]

what am trying to accomplish is whenever am assigning any device with ip let's say 10.10.10.10 then the multicast ip should be 10.10.10.11..

[Peter Paluch]

Hello Mohamad,

As John has explained already, correct multicast addresses are only in the range 224.0.0.0 - 239.255.255.255. In fact, a packet is recognized as multicast if and only if its destination address is within this range. There is no way to make a different address a multicast address.

But the question that John also gave you - and you did not answer it satisfactorily - is what should be accomplished, i.e. what shall be the result, or the working effect, of "assigning the multicast ip of 10.10.10.11"? What is what you are trying to do by inventing multicast addresses like these for individual stations?

Best regards,

Peter

[mfouad.jahmi]

i got your point now, i was little bit confused on the range which has to be the same as you have described. well now i better follow your advice. i will make the range of the devices starts with 239.246.39.(31-254) and the multicast ip should match that range as 239.246.39(32-254). so basicly now what i am trying to accomplish is to set-up the multicast ip address last octect increamented by one when comparing with any station.

so what are the proceedures to follow ?

thanks a lot for your support

[Peter Paluch]

Mohamad,

i will make the range of the devices starts with 239.246.39.(31-254) and  the multicast ip should match that range as 239.246.39(32-254).

You can't do this. A station can never be configured with a multicast IP address as its own IP address. The operating system will not allow you to configure it this way. A station can have an IP address only in the "normal" range of 1.0.0.0 - 223.255.255.255. The multicast IP address range is reserved exclusively to describe multicast groups, and can never be assigned to any individual station.

what i am trying to accomplish is to set-up the multicast ip address  last octect increamented by one when comparing with any station.

This is impossible to achieve. The addressing principles in IP simply do not allow this kind of address assignment. Why would you want a station to have its own IP address one step less than the multicast group it is subscribed into, anyway?

Please note that in order for a station to receive a multicast stream, its own IP address can be arbitrary. The process of subscribing to a multicast group (and starting to listen on a particular destination multicast IP address) is totally unrelated to the real IP address of the station.

Best regards,

Peter