ha. you're not the only one. Took our my books last night to start reading on 
this. The road to written v5 could be  a long one 

:) 

Good luck all with your studies. 
B

> From: [email protected]
> Date: Wed, 8 Jan 2014 08:33:09 -0500
> To: [email protected]
> CC: [email protected]
> Subject: Re: [OSL | CCIE_RS] Multicast question
> 
> Aaaaaand it's official: I've forgotten *everything* related multicast since 
> my pass :-(
> 
> They always say you're not half-pregnant with multicast -- you either work 
> with it every day, or never. I'm in the "never" camp...
> 
> Bob
> -- 
> Sent from my iPhone, please excuse any typos.
> 
> > On Jan 7, 2014, at 6:01 PM, Tony Singh <[email protected]> wrote:
> > 
> > 
> > MSDP and MBGP (multicast BGP) are independent of each other but required 
> > for inter-domain multicast, MSDP enables PIM-SM domain RP's to share source 
> > information via sa-cache messages (S,G) via a TCP connection to each other, 
> > the cases where you wouldn't use MBGP with MSDP would be an anycast 
> > implementation via some IGP domains
> > 
> > MSDP control-plane RPF checks are ignored if we have just two peers, if we 
> > have more then two peers then the originator-id is checked to ensure its 
> > own RP address is not originating the message in which case it would fail 
> > (if no originator-id is selected then preference is given to the loopbacks)
> > 
> > If you get a question where a restriction of not changing IGP AD/metric or 
> > static mroute is imposed and IF the topology permits it then create a MBGP 
> > peer to originate the source of the multicast feed and also the RP address, 
> > this way you can route around the RPF failure.
> > 
> > Order of preference for RPF checks are as follows:
> > 
> > Static mroutes
> > DVMRP routes
> > MBGP routes
> > Unicast routes
> > 
> > So as you can see MBGP routes are preferred for RPF over unicast, you still 
> > need to ensure PIM is enabled on the relevant data-planes for this to work!
> > 
> > --
> > BR
> > 
> > Tony
> > 
> > Sent from my iPad
> > 
> >> On 7 Jan 2014, at 20:08, "Ryanlk18 ." <[email protected]> wrote:
> >> 
> >> You can use MPBGP multicast address-family to carry source information
> >> across the network to the RP.  This can be useful in dealing with RPF
> >> issues where static mroutes won't work or you cannot manipulate the
> >> underlying routing protocol.
> >> 
> >> MSDP is used to connect RPs together across multicast domains.  This is
> >> needed when you have multiple multicast domains that need to be connected
> >> in order to share multicast feeds across the network.
> >> 
> >> It could be possible to peer MSDP through a GRE Tunnel, but I've always
> >> used MSDP and MPBGP together as they are both necessary to carry the source
> >> and RP information to bridge the domains.
> >> 
> >> V/r,
> >> 
> >> Ryan Krcelic
> >> 
> >> 
> >> 
> >>> On Tue, Jan 7, 2014 at 2:31 PM, Andrew LaPorte <[email protected]> wrote:
> >>> 
> >>> I'm going to try to help out here a bit.
> >>> 
> >>> BGP and MSDP are not directly related to one another.  You can have MSDP
> >>> without having BGP but it is typical to have BGP and Multicast as that is 
> >>> a
> >>> larger environment.
> >>> 
> >>> MSDP simply allows one RP to exchange multicast information with another
> >>> RP,
> >>> i.e. source A can register with RP A then another source B can register
> >>> with
> >>> RP B.  If RP A and RP B have MSDP between them then both with know about
> >>> source A and source B.
> >>> 
> >>> Now if you want a client to be able to get to both source A and source B
> >>> they must have a route that passes an RFP check. This is where BGP or OSPF
> >>> or EIGRP would come in typically.
> >>> 
> >>> Hope this helps.
> >>> 
> >>> AndyL
> >>> 
> >>> 
> >>> -----Original Message-----
> >>> From: [email protected]
> >>> [mailto:[email protected]] On Behalf Of Ryan Jensen
> >>> Sent: Tuesday, January 7, 2014 1:47 PM
> >>> To: [email protected]
> >>> Subject: [OSL | CCIE_RS] Multicast question
> >>> 
> >>> I all, this is probably an amateur question, but I'm having an issue
> >>> wrapping my head around how BGP for multicast relates to MSDP.
> >>> Here's how I Think they relate:
> >>> BGP for multicast shares routes to RPs for the purpose of RPF MSDP shares
> >>> 'routes' to multicast sources.
> >>> 
> >>> The sources that are shared via MSDP need to be reachable via the routes
> >>> learned from BGP yes?
> >>> 
> >>> Is this a correct understanding?
> >>> _______________________________________________
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> >>> 
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