[c-nsp] IOS XR needs PIM&MLD for clients to receive multicast stream

[Adam Vitkovsky]

Hi Mikael,

Have you enabled the CE facing interfaces under "router igmp" please? (oh and XR uses IGMPv3 by default).
- but can't recall if it worked at the end or the PIM was indeed necessary.  


adam
> -----Original Message-----
> From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
> Mikael Abrahamsson
> Sent: 09 February 2015 14:28
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] IOS XR needs PIM&MLD for clients to receive multicast
> stream
> 
> 
> Hi,
> 
> I am re-learning multicast for the 3-4th time in the past 10 years now so
> I'm rusty.
> 
> IOS XR machine (ASR9k). PIM-SSM (group in ff38::/96)
> 
> multicast-source--R1--R2--R3--client
> 
> This is R3:
> 
> multicast-routing
>   address-family ipv6
>    interface-inheritance disable
>    interface all enable
> 
> I enable the interface in "router pim" and "router mld", and everything is
> fine, client can receive multicast stream after MLD join, mrib of course
> looks great.
> 
> Why can't I now disable PIM? Why is PIM needed on a client-only interface
> wherefrom I don't need any multicast sourced, just want clients to be able
> to MLD join streams from elsewhere. If I disable PIM, mrib still looks
> almost the same, but there is no multicast being forwarded out that
> interface towards the client.
> 
> I really would like to avoid having to run PIM on thousands of
> (sub)interfaces, which on top of everything needs to be protected with an
> ACL because I don't want my customers to be able to establish a PIM
> session with my router.
> 
> Without PIM:
> 
> #show mrib ipv6 route <source-IPv6-address>
> Mon Feb  9 15:17:16.770 CET
> 
> IP Multicast Routing Information Base
> Entry flags: L - Domain-Local Source, E - External Source to the Domain,
>      C - Directly-Connected Check, S - Signal, IA - Inherit Accept,
>      IF - Inherit From, D - Drop, ME - MDT Encap, EID - Encap ID,
>      MD - MDT Decap, MT - MDT Threshold Crossed, MH - MDT interface
> handle
>      CD - Conditional Decap, MPLS - MPLS Decap, MF - MPLS Encap, EX -
> Extranet
>      MoFE - MoFRR Enabled, MoFS - MoFRR State, MoFP - MoFRR Primary
>      MoFB - MoFRR Backup, RPFID - RPF ID Set
> Interface flags: F - Forward, A - Accept, IC - Internal Copy,
>      NS - Negate Signal, DP - Don't Preserve, SP - Signal Present,
>      II - Internal Interest, ID - Internal Disinterest, LI - Local Interest,
>      LD - Local Disinterest, DI - Decapsulation Interface
>      EI - Encapsulation Interface, MI - MDT Interface, LVIF - MPLS Encap,
>      EX - Extranet, A2 - Secondary Accept, MT - MDT Threshold Crossed,
>      MA - Data MDT Assigned, LMI - mLDP MDT Interface, TMI - P2MP-TE MDT
> Interface
>      IRMI - IR MDT Interface
> 
> (<source>,<group>)
>    RPF nbr: fe80::da67:d9ff:fe4b:510c Flags:
>    Up: 00:00:09
>    Incoming Interface List
>      HundredGigE0/0/0/0 Flags: A, Up: 00:00:09
>    Outgoing Interface List
>      TenGigE0/2/0/3.2021 Flags: LI, Up: 00:00:09
> 
> When I enable PIM, I get:
> 
>    Outgoing Interface List
>      TenGigE0/2/0/3.2021 Flags: F NS LI, Up: 00:01:59
> 
> Now everything works as it should.
> 
> and when I disable PIM, it goes back to:
> 
>    Outgoing Interface List
>      TenGigE0/2/0/3.2021 Flags: LI, Up: 00:02:36
> 
> F means "Forward", so it's pretty obvious that the forwarding plane stops
> the forwarding of this multicast group without PIM enabled on the
> interface. I just don't understand why.
> 
> Could someone please enlighten me?
> 
> --
> Mikael Abrahamsson    email: swmike at swm.pp.se
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