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New Member

igmp between PIM routers in a PIM-SM domain

on our network we have 2 6509 both in a PIM-SM domain one of the 6509s been the RP. a single vlan connects the 2 6509 switches together at layer 3. then edge routers running pim-sm connect to the 6509s via single vlans. all vlans run igmp snooping. i have noticed that igmp is prooning back the flooding of the traffic at layer 2 does anyone know how this is working as there is no igmp traffic between any of the routers or 6509s.

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

Re: igmp between PIM routers in a PIM-SM domain

hi,

ANS:"If a multicast group has only sources and no receivers in a VLAN, IGMP snooping constrains the multicast traffic to only the multicast router ports."and ur CLIENT is connected to ROUTER.and ROUTER is connected to SWITCH,Switch connected to another router where source is connected.SO SWITCH WILL LISTEN ROUTER PORTS AND WILL HAVE AN ENTRY IN MULTICAST TABLE.

hope this will help.

5 REPLIES
New Member

Re: igmp between PIM routers in a PIM-SM domain

Hi,

IGMP snooping restricts multicast traffic that exits through the LAN ports to which hosts are connected. IGMP snooping does not restrict traffic that exits through the LAN ports to which one or more multicast routers are connected.

if this is not the answer,then i misunderstood.then clearify ur question.

New Member

Re: igmp between PIM routers in a PIM-SM domain

sorry think my question isnt clear, If I have a 2950 switch with 2 routers connected to the switch via there eth0 interface all on vlan 1. the switch has no other devices connected to it and has igmp snooping enabled on vlan 1.

if one router has a multicast source on its eth1 interface and the other router has a multicast client on its eth1 interface interested in the multicast source.

the 2 routers are in a single PIM-SM domain.

how does the 2950 switch handle the multicast. when i do a show mac-address-table multicast I have an entry for the multicast group sourced from the other side of one of the routers. it says its learnt through igmp. how is this as igmp is between the client and local router.

any help is appreciated as I have been readin up on this for ages and cant find an answer.

Regards, Kev

New Member

Re: igmp between PIM routers in a PIM-SM domain

I have attached a digram of an example of what i meen.

Regards

Kev

New Member

Re: igmp between PIM routers in a PIM-SM domain

hi,

ANS:"If a multicast group has only sources and no receivers in a VLAN, IGMP snooping constrains the multicast traffic to only the multicast router ports."and ur CLIENT is connected to ROUTER.and ROUTER is connected to SWITCH,Switch connected to another router where source is connected.SO SWITCH WILL LISTEN ROUTER PORTS AND WILL HAVE AN ENTRY IN MULTICAST TABLE.

hope this will help.

New Member

Re: igmp between PIM routers in a PIM-SM domain

thankyou for the response it answers my question.

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