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Help with basic Multicast

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

2 REPLIES
Bronze

Re: Help with basic Multicast

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.

Hall of Fame Super Silver

Re: Help with basic Multicast

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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