Multicast PIM Accept Register

Lessons Discussion
1

This topic is to discuss the following lesson:

https://networklessons.com/multicast/multicast-pim-accept-register/

2

Hi Rene,

I setup up lab for 4 routers to allow one router and block other router, it’s not working, but for two routers like your lab its working.
PIM Accept-Register LAB

in this LAB I want to filter R1 as source to R4 which is configured group address 239.9.9…9, but its allowing all sources.

Configuration

R1

interface GigabitEthernet1/0
 ip address 12.12.12.1 255.255.255.0
 ip pim sparse-mode
 negotiation auto
end
!
ip pim rp-add 2.2.2.2

R2

interface GigabitEthernet1/0
 ip address 12.12.12.2 255.255.255.0
 ip pim sparse-mode
 negotiation auto
!
interface GigabitEthernet2/0
 ip address 24.24.24.2 255.255.255.0
 ip pim sparse-mode
 negotiation auto
!
interface FastEthernet0/0
 ip address 23.23.23.2 255.255.255.0
 ip pim sparse-mode
 duplex half
!
ip pim rp-address 2.2.2.2
ip pim accept-register list Source
!
interface Loopback0
 ip address 2.2.2.2 255.255.255.255
 ip pim sparse-mode
!
ip access-list extended Source
 deny   ip host 12.12.12.1 host 239.9.9.9
 permit ip any any
3

Hi Rene,

I setup same LAB in VIRL, the previous LAB was GNS3, right now its showing this debug message

Aug 22 05:13:25.023: %PIM-4-INVALID_SRC_REG: Received Register from 2.2.2.2 for (12.12.12.1, 239.9.9.9), not willing to be RP

from R2 (Which is the RP), but even though I’m receiing INVALID-Source address its still allowing to ping the group address and even setting up in multicast routing.

(12.12.12.1, 239.9.9.9), 00:02:26/00:00:33, flags: FT
 
 Incoming interface: GigabitEthernet0/1, RPF nbr 12.12.12.1
  Outgoing interface list:
    GigabitEthernet0/2, Forward/Sparse, 00:02:26/00:02:04

Regards
Jama

4

Hi Rene

I changed topology this way its working without Issue

image

Why its accepting R1 as source and not accepting Source Router as Source ?

the difference between the Source router and R1 is that the Source router isn’t running any PIM mode, I just enabled ip multicast-routing. (and sure I modified the Access-list)

is this means that if the DR it self generates multicast traffic as source, the Pim Accept Register will not effect it?.

Regards
Jama

5

Hi Jama,

It’s probably because the pings are sent from the G1/0 interface on the R1 router. When R2 doesn’t accept 12.12.12.1 as a source, it sends a prune message to R1 so that it doesn’t forward this multicast traffic anymore. R1 however, is sourcing the traffic from its G1/0 interface so it’s not “multicast routed”.

If you source the multicast traffic from a loopback interface on R1 that isn’t permitted on the access-list of R2, you’ll see that R1 no longer forwards it on its G1/0 interface because of the pruning.

Rene

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