Help with basic Multicast

Unanswered Question
Mar 13th, 2009
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Hi


I'm new to multicasting so I'm confused about the following. When I run "Show ip mroute" I get the following:


(10.45.8.34, 239.255.3.20), 11:28:59/00:02:53, flags: TA

Incoming interface: Vlan8, RPF nbr 0.0.0.0, RPF-MFD

Outgoing interface list:

Vlan11, Forward/Sparse, 00:57:11/00:02:23, H


(10.45.8.35, 239.255.3.20), 11:28:57/00:02:53, flags: TA

Incoming interface: Vlan8, RPF nbr 0.0.0.0, RPF-MFD

Outgoing interface list:

Vlan11, Forward/Sparse, 00:57:11/00:02:23, H, A


(10.45.8.36, 239.255.3.20), 11:29:01/00:02:53, flags: TA

Incoming interface: Vlan8, RPF nbr 0.0.0.0, RPF-MFD

Outgoing interface list:

Vlan11, Forward/Sparse, 00:57:11/00:02:23, H, A


As far as I can see vlan 8 is sourcing the traffic and for some strange reason sending it through to vlan 11. Can some one explain why that would happen and what kind of filter I can place to stop multicast jumping between vlan 8 and vlan 11 both ways?


Thanks in advance.

Dan

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JamesLuther Fri, 03/13/2009 - 06:55
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Hi Dan,


Are you running PIM on your Vlan 11 interface? What's the output of


sh ip pim neighbor

sh ip pim rp

sh ip pim interface

sh run int vlan 11


There must be a multicast reciever downstream that is requesting these groups as you're using sparse mode.



Giuseppe Larosa Fri, 03/13/2009 - 07:08
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Hello Dan,


>> what kind of filter I can place to stop multicast jumping between vlan 8 and vlan 11 both ways?


for stopping all multicast traffic you need to go to interface vlan 11 and you need to disable pim


int vlan 11

no ip pim sparse-mode


be aware that at least another multicast capable router/switch exists in vlan 11 because the A flag means assert winner


so you need to do so also on SVI vlan11 of the other router


if you want to stop only traffic from 239.x.y.z from entering vlan 11


ip igmp access-group xx


xx standard acl that can deny 239 range


again in both routers


if out vlan11 there are downstream routers you need


ip multicast boundary access-list [filter-autorp]


see


http://www.cisco.com/en/US/docs/ios/ipmulti/command/reference/imc_03.html#wp1029655


use sh ip pim interface

sh ip pim neighbors


to find out pim neighbors in vlan11


Hope to help

Giuseppe


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