Filter multicast group advertisement on outgoing advertisement.

[Lovleen Arora]

Hi,

I have had very minimal experience with IP multicast, so asking for some help here.

We have 2 requirements in our network:

1. There is present multicast running in the network. We have 2 WAN connections from our main router which is the rp. as per below commands I understand (correct me if I am wrong). We want to extend multicast to out WAN links, but only send the groups (239.10.0.0/24, and 239.20.0.0/24) and nothing else. I could not find anything that will do outbound filtering on the interface for multicast advertisement.

Main-rtr config below:

#ip pim autorp listener

#ip pim send-rp-announce Lo5 scope 16

#ip pim send-rp-discovery scope 6

2. We have 2 subnets which send the multicast join requests to the RP. What can we do so the RP only entertains join-requests from the defined 2 subnets (10.20.30.0/24, and 10.20.40.0/24)

I understand this is possible if I add the below commands to the RP router, but if you can validate that plz, it will be good. many thanks

commands for #2.

ip pim accept-register list <list-name>

ip access-list ext <list-name>

permit ip 10.20.30.0 0.0.0.255 any

permit ip 10.20.40.0 0.0.0.255 any

thanks in advance for you time and help.

Lovleen

[Peter Paluch · Accepted solution]

Hi Lovleen,

I believe that the requirement 1 can be solved using the ip multicast boundary command on the WAN interfaces. This command allows you to define the senders and multicast groups for which the multicast traffic will be received and accepted (the in direction), and for which the multicast can be forwarded out (the out direction). Please have a look at the following documentation:

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti/command/imc-cr-book/imc_i2.html#wp6515743030

As for the requirement 2, the solution is syntactically okay but please allow me one question: Are those two subnets 10.20.30.0/24 and 10.20.40.0/24 directly connected to the RP, or are they located behind a different router in your topology?

Best regards,
Peter

[Lovleen Arora]

Hi Peter,

Thanks for number#1.

I have prepared the following script for it.

RP-router:

ip access-list stand 10

interface gig3/12

description wan-link

ip pim sparse-mode

ip multicast boundary 10 out

on the wan router

inter gi1/0/48

ip pim sparse-mode

For #2.

the 2 source subnets (10.20.30.0/24 and 10.20.40.0/24) are not directly connected to RP and there are other L3 devices in between which also have multicast configured on them.

many thanks

Lovleen

[Lovleen Arora]

Hi,

any response abt #2?

Thanks

[Peter Paluch]

Hi Lovleen,

I apologize for responding so late. The last two weeks were busy. My sincere apologies.

The solution for issue #2 is correct - the reason I've asked was that if those two networks were directly connected to the RP, we would need to use direct ACLs or multicast boundaries to filter off the unwanted networks. That is also valid if the RP directly connects to other networks with possible sources - these would need to be taken care of using ACLs or multicast boundaries. Is the RP purely an internal router connected only to other router, or does it also connect to end networks?

Best regards,
Peter