Re: FabricPath & PIM-SM Interoperation (OT)

Hi Brian,

Thanks for you response. I've read these two documents before, I really
wish they went deeper.

My question is more about the control plane signalling.

Imagine you have a host connected to a FP-Edge Port (Classic Ethernet), it
sends out an IGMP-Membership report for group X. The FP switch it is
connected to then generates a GM-LSP. On your core switch, you have an SVI
with OSPF and PIM-SM enabled, to connect to some legacy part of your
network. I would assume that the core switch should send out a PIM-Join
message on the PIM-SM enabled SVI ( Assuming the RP is upstream from that
interface). The same question applies to multicast traffic received, on a
FP-Edge Port.

Thanks again,

-YuriB

On Wed, Sep 18, 2013 at 1:08 PM, Brian McGahan <bmcgahan_at_ine.com> wrote:

> Multicast senders or receives couldn't be "inside" the FabricPath per-se,
> they have to be on Classical Ethernet ports. Is your question about the
> control plane signaling or the data plane flow? For the control plane the
> PIM Join messages are multicast, so they should follow the multicast
> multidestination tree in the Fabric Path core. PIM Register is unicast so
> it should follow the normal unicast path through the FP core based on the
> MAC address of the RPF neighbor for the RP.
>
> In reality I think that multicast was a small afterthought for a lot of
> these DC specific technologies like FabricPath and vPC. ECMP with
> multicast is problematic to begin with though, so with FabricPath their
> workaround was just to build 2 multidestination trees, and then hash
> between the two of them. Remember with vPC, the Peer-Link *is* in the data
> plane for all multicast flows, not just the control plane. I'm assuming
> this is the same for vPC+ with FabricPath, because there's no other way to
> account for receivers on orphan ports.
>
> You're right though, the docs are sparse (no pun intended). The only
> things I could find on the external documentation was these two:
>
> Cisco FabricPath Design Guide: Using FabricPath with an Aggregation and
> Access Topology - Multicast Routing Considerations
>
> http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/guide_c07-690079.html#wp9000345
>
> FabricPath Forwarding - Forwarding Multicast Packets
>
> http://www.cisco.com/en/US/docs/switches/datacenter/sw/5_x/nx-os/fabricpath/configuration/guide/fp_forwarding.html#wp1804761
>
>
>
> Brian McGahan, 4 x CCIE #8593 (R&S/SP/SC/DC), CCDE #2013::13
> bmcgahan_at_INE.com
>
> Internetwork Expert, Inc.
> http://www.INE.com
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Yuri Bank
> Sent: Wednesday, September 18, 2013 1:59 PM
> To: Cisco certification
> Subject: FabricPath & PIM-SM Interoperation (OT)
>
> Hello everyone,
>
> I posted this on c-nsp, and really didn't get the kind of answers I was
> looking for. Hopefully there is someone out there that can dive a little
> deeper into this topic.
>
>
> Basically, I would like to know the details on how a switch running FP
> (Nexus 7k or 5k) deals with multicast sources/listeners that are inside a
> FP domain, when it is running PIM-SM on a L3 interface(SVI) that is
> connected to some other part of the network ( that isn't running FP).
>
> For example, my understanding is that a FabricPath edge switch will flood
> GM-LSPs if it has an interested listener for a multicast group. When the FP
> switch that is also running PIM-SM on its L3 interface sees this, it would
> make sense for it to send a PIM-Join message to its neighbor, toward the
> RP. The same thing should happen with multicast sources, and PIM Register
> messages.
>
> Does anyone have experience with this? Is my assumption correct here? Any
> details would be appreciated, as the Cisco documentation on this topic is
> quite limited.
>
> Thanks,
>
> YuriB.
>
>
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Received on Wed Sep 18 2013 - 13:49:50 ART