IGMP groups

[Jon Marshall]

Why are you trying to leave that group ? 

Jon

[TekashiSixNine]

I want one router to be in two groups (224.0.1.40 and other for example 225.2.2.2) and the other two routers to be only in one of those two groups

[Jon Marshall]

That group address is a well know group address used by PIM for RP discovery so not sure you can leave it even if you wanted to. 

Jon

[Giuseppe Larosa]

Hello @TekashiSixNine ,

224.0.1.39 and 224.0.1.40 are used by Cisco proprietary Auto RP that is a way to dynamically advertise RP to groups mappings.

One is used by candidate RPs and one is used by the mapping agent that makes a choice of the best RP for a given group G in ASM any source Multicast

To be noted in PIMv2 the bootstrap protocol can be used to elect a BSR, the BSR message travels hop by hop i.e it is another type of PIM message.

To be noted in a network for different groups G you can have at the same time:

link local multicast 224.0.0.x this are not routed and they have TTL=1

ASM sparse mode

ASM sparse-dense mode

PIM Bidirectional

PIM SSM Source Specific Multicast groups  that requires IGMPv3 on hosts

Hope to help

Giuseppe

[paul driver]

Hello

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@TekashiSixNine wrote:

 My question is which command should I use to leave this group because I have tried the command "no ip igmp join-group 224.0.1.40" but with no result

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Use pim dense mode, 224.0.1.40 it has no meaning in this mode as no RP discovery is made, however it is still aactive even in this mode, tbh no sure how you can turn it off unless you try an acl:

ip access-list standard norpdiscovery
deny 224.0.1.40.
permit any

int x/x
ip igmp access-group norpdiscovery