Re: igmp querier , assert winner and DR confusion on election

Thanks for the reply Mark,
but i still dont get the function of the DR. How does it differ from the
querier? anybody!

Regards,

On Fri, Dec 10, 2010 at 9:32 PM, Mark_1982 <m.abghany_at_gmail.com> wrote:

> Hi there
>
> u have 3 phases of elections:
>
> 1-Querier elections, who will handle the communication between a group of
> hosts and a group of routers on the same segment
> 2-Designated Router Elections, who will handle the quey message (Multicast
> signalling)
> 3-Desingated Forwarder, who will handle Multicast traffic (video stream for
> example)
>
> First the Querier Election Process.
> At start up each router sends a query message to the all systems group
> 224.0.0.1 from its own interface address. The router with the lowest ip
> address is elected IGMP querier.
>
> Second the PIM DR Election Process
> The router with the highest ip address is elected as PIM DR. This
> selection process can also be influenced by configuring a pim DR priority.
> By default all routers have priority 1, hence highest ip address wins by
> default. However if DR priority is used then highest DR priority wins.
>
> The show igmp interface command can be used to show elected DR and querier
>
> *Third the Forwarder Election Process ( u will need to use Assert
> messaging as an election mechanism)*
> These Assert Messages are used to elect the PIM forwarder using the
> following three rules:
>
> 1. The router generating an Assert with the lowest Administrative
> distance is elected the forwarder. The AD would only differ if the
routes
> to R5 where from different routing protocols. If the Administrative
> Distances are the same then we move to step 2.
> 2. The best unicast routing metric is used to break a tie if the
> Administrative Distances are the same. The combination of AD and the
> unicast routing metric is referred to as a tuple. If metrics are the
same
> them we move on to step 3.
> 3. The device with the highest IP Address will be elected as the PIM
> Forwarder.
>
> *Note:*u can make the three routers the same router with some manipulation
> in priority or IGP, but they are NOT the same functions, its administrative
> issue to be the same router or not
>
> BR/Mark
>
> On Thu, Dec 9, 2010 at 12:32 AM, ehtesham ali
<conect2ehtesham_at_gmail.com>wrote:
>
>> thanks Babola ,
>> sure experts will help ! eagerly waiting for their comments ! just to
>> point
>> out that DR is ONLY used for Registration and sending IGMP join.
>>
>> Being DR doesn't mean that it will always be forwarder .
>>
>> Regards
>> On Wed, Dec 8, 2010 at 11:29 PM, Bobola Oke <okebobola_at_gmail.com> wrote:
>>
>> > I highly recommend you study TCP/IP routing vol2. Deff Doyle does a
>> > fantastic job of explaining these clearly.
>> >
>> > For assert elections, the router with the lowest cost to the source
>> always
>> > wins.
>> >
>> > The designated router is the forwarder. (I'm not sure on this... I think
>> I
>> > need to refer to the book myself :D). The IGMP querier checks if there
>> are
>> > hosts that want to receive multicast traffic. The forwarder does the
>> > forwarding :D
>> >
>> > If all the cost to reach the source were to be the same. R3 would be the
>> > designated router (forwarder) and R1 would be the querier. I think the
>> rule
>> > changes if IGMP version 1 and PIM v1 is being used.
>> >
>> > I'm sure the experts can help further on this! Just trying to do my
>> bit...
>> >
>> >
>> >
>> >
>> > On Wed, Dec 8, 2010 at 4:54 PM, imran ali <immrccie_at_gmail.com> wrote:
>> >
>> > > hi group ,
>> > >
>> > > R1 , R2 , R3 are connected on a multiaccess segment sharing ip
>> address
>> > > from
>> > > 10.1.123.X /24 subnet where X is the router no .
>> > >
>> > > now when it comes to cost R2 is having lowest cost to reach the SOURCE
>> .
>> > >
>> > > All the router has equal cost to Rp. igmp ver is 2
>> > >
>> > > question :
>> > >
>> > > 1) who will be elected as assert forwarder ? DR ? Igmp Querier ?
>> > >
>> > > 1) I believe all three roles are seprate or is there any overlap of
>> > roles?
>> > >
>> > > i have read some where that igmp querier is the one who forwards the
>> > > traffic on LAN but in my case R2 should be
>> > > the Mcast data forwarder .
>> > >
>> > > Regards
>> > >
>> > >
>> > > Blogs and organic groups at http://www.ccie.net
>> > >
>> > >
>> _______________________________________________________________________
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>> > >
>> > >
>> > >
>> > >
>> > >
>> > >
>> >
>> >
>> > --
>> > Bobola Oke
>> >
>> >
>> > Blogs and organic groups at http://www.ccie.net
>> >
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>> > Subscription information may be found at:
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>>
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>

--
Bobola Oke
Blogs and organic groups at http://www.ccie.net