From: Danshtr (danshtr@gmail.com)
Date: Wed May 04 2005 - 12:28:48 GMT-3
To sum it UP:
On this diagram: http://metawire.org/~danshtr/pim.png
Who will forward packets from the SENDER? RA or RB?
RA will be the pim- DR (higher IP Address 1.1.1.2)
RB will be IGMP querier (lowesr IP Address 1.1.1.1)
RB is closer to the RP so i guess packet arriving to the SENDER should
use RB, and RA should send purn to RD.
On 5/4/05, Jim <quangnn@hptvietnam.com.vn> wrote:
> Multicast traffic always flows from source to client. Routers send Querry
> message to determine if there is any
> multicast client on segment and clients answer the querry with Membership
> Report which has Multicast Group Address as destination address.
> Base on the status of client and multicast group address, the router starts
> to send joins up the tree to RP ( shared tree) or the source ( source tree)
> for multicast feed.
>
> HTH,
>
> Jim
>
> ----- Original Message -----
> From: "Danshtr" <danshtr@gmail.com>
> To: "ccie2be" <ccie2be@nyc.rr.com>
> Cc: "Jim" <quangnn@hptvietnam.com.vn>; "Cisco certification"
> <ccielab@groupstudy.com>
> Sent: Wednesday, May 04, 2005 8:33 PM
> Subject: Re: Multicast DR...
>
> Maybe I am missing something, all the answers are about who send
> packets into the share media LAN.
>
> But what about packets comming _from_ the LAN?
>
> If there are two routers on a shared media LAN, running PIM-SM, which
> one will forward the muticast traffic _from_ the shared media LAN?
>
> On 5/4/05, ccie2be <ccie2be@nyc.rr.com> wrote:
> > Hi Jim,
> >
> > If there are 2 pim SM routers on a Lan segment either of which could
> > potentially sends joins up the shared tree to the RP, however, only 1 of
> > those routers has a path to the RP, make sure the router with a path to
> > the
> > RP is the DR. Recall that the pim router with the highest ip address
> > becomes the DR and that only the DR sends joins up the tree to the RP. If
> > the DR doesn't have a path to the RP, the joins won't ever get to the RP
> > and
> > mcast traffic won't ever flow down the tree. To see which of the 2
> > routers
> > on the segment is the DR, do a show ip pim nei. If the output shows "(DR)"
> > on the right side of neighbor's entry, then that nei is the DR. One way to
> > change which router becomes the DR is to change the ip addresses of the
> > interfaces on the lan segment such that the preferred DR has the highest
> > IP
> > address. A better way is to use the interface command, ip pim dr-priority
> > #.
> >
> > In a DM network where 2 or more pim routers on LAN could potentially send
> > mcast pkts onto the lan segment, DM pim prevents this by electing a
> > forwarder - a rtr which will send the mcast traffic onto the lan. 1st,
> > the
> > AD of the route to the source is compared and the route with the lowest AD
> > wins. If the AD's are equal, then the metric of the route is compared and
> > the lowest metric wins. If there's still a tie, the ip address is the
> > tiebreaker.
> >
> > HTH, Tim
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > Jim
> > Sent: Wednesday, May 04, 2005 7:20 AM
> > To: ccie2be; 'Danshtr'; 'Cisco certification'
> > Subject: Re: Multicast DR...
> >
> > Tim,
> >
> > Thanks for getting back to me,
> >
> > so which one will sends joins up the tree if 2 routers are on the
> > shared-media with client?
> >
> > R1 R2
> >
> > ----|-------|-------
> >
> > |
> >
> > client
> >
> > the proccess of PIM forwarder election works with both pim dense & spare
> > mode and it happens whenever one of the router receive multicast packets
> > on
> > its outgoing interface for that packet's group.
> >
> > When the client sends join message to R2, R2 joins shared tree and the
> > traffic will flow from source to client this way. But when R2 forwards
> >
> > traffic with destination address as multicast packets to clients, switch
> > will treats these packets as broadcast and forward to all other ports. As
> > the result, R1 receives packets on its outgoing interface for that
> > packet's
> > group and it immediately starts the proccess of PIM forwarder election by
> > sending assert message. Finally, the winner will join the shared tree and
> > take the role of the forwarder for all clients on the shared media.
> >
> > On TCP/IP vol2 489, we have "the election of designated router on
> > multiaccess networks are common to PIM-SM and PIM-DM"
> >
> > Jim.
> >
> > ----- Original Message -----
> > From: "ccie2be" <ccie2be@nyc.rr.com>
> > To: "'Jim'" <quangnn@hptvietnam.com.vn>; "'Danshtr'" <danshtr@gmail.com>;
> > "'Cisco certification'" <ccielab@groupstudy.com>
> > Sent: Wednesday, May 04, 2005 4:53 PM
> > Subject: RE: Multicast DR...
> >
> > > Jim,
> > >
> > > I think your remarks are correct only if PIM Dense Mode is being used.
> > >
> > > If PIM Sparse Mode is used, then the rtr which sends joins up the tree
> > > will
> > > also forward mcast traffic to hosts.
> > >
> > > HTH, Tim
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > > Jim
> > > Sent: Wednesday, May 04, 2005 5:27 AM
> > > To: Danshtr; Cisco certification
> > > Subject: Re: Multicast DR...
> > >
> > > On a shared media, the router selected to forward traffic to client is
> > > the
> > > one
> > >
> > > i) who advertises lowest metric preference ( in other words, lowest AD)
> > > ii) who advertises lowest metric if the metric preference is equal
> > > iii) who has the highest IP address on the network if all other metric
> > > are
> > > the same.
> > >
> > > PIM bases on other protocols for its routing so you can verify DR
> > > selection
> > > by checking the route to Multicast Source in routing and mroute table.
> > >
> > > HTH, Jim
> > >
> > > ----- Original Message -----
> > > From: "Danshtr" <danshtr@gmail.com>
> > > To: "Cisco certification" <ccielab@groupstudy.com>
> > > Sent: Wednesday, May 04, 2005 1:47 PM
> > > Subject: Multicast DR...
> > >
> > >
> > >> Hello
> > >>
> > >> Reading through multicast documentation, they are mentioning DR and
> > >> queriers which both are intended for deciding which router will
> > >> forward multicast packets to the recievers.
> > >>
> > >> But i couldn't find how the routers, on a shared media, decide which
> > >> one will forward the packets from the source.
> > >>
> > >> Does anyone here knows the answer? I am sure there is... because it
> > >> works!
> > >>
> > >> --
> > >> Best regards,
> > >> Dan
> > >>
> > >> _______________________________________________________________________
> > >> Subscription information may be found at:
> > >> http://www.groupstudy.com/list/CCIELab.html
> > >
> > > _______________________________________________________________________
> > > Subscription information may be found at:
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> > >
> > > _______________________________________________________________________
> > > Subscription information may be found at:
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> >
> > _______________________________________________________________________
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> >
> >
>
> --
> Best regards,
> Dan
>
>
-- Best regards, Dan
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