Re: Multicast Understanding

Dear Gents,

I got it guys.The thing that I wasn't clearly able to understand is that
there are infact two seperate streams (one from 12.0.0.1/and one from
13.0.0.1). For each of those streams the forwarder election took place based
on:

1.Better Administrative distance to the source
2.Better metric to the source.
3.Highest IP address.

Thus for source 12.0.0.1 the forwarder was R2 (as it is connected to it) and
for source 13.0.0.1 the forwarder was R3.

Thank You for your support & help!

Best Regards,

On Mon, Oct 12, 2009 at 9:34 AM, karim jamali <karim.jamali_at_gmail.com>wrote:

> Dears,
>
> R1 is acting as server,R4 as client. I used debug ip mpacket on R4,and
> saw two packets came from the two interfaces of R1(
> 12.0.0.1/13.0.0.1). And I used debug ip mpacket on R2 and R3 and both
> showed a forwarded packet to the segment.
>
> Please I really need to understand what is going on thus I will paste the
> configs:
>
> R1
> ip multicast-routing
> interface Serial1/0
> ip address 12.0.0.1 255.255.255.0
> ip pim sparse-mode
> serial restart-delay 0
> clock rate 64000
> !
> interface Serial1/1
> ip address 13.0.0.1 255.255.255.0
> ip pim sparse-mode
> serial restart-delay 0
> clock rate 64000
>
> router ospf 1
> log-adjacency-changes
> network 0.0.0.0 255.255.255.255 area 0
>
> ip pim rp-address 2.2.2.2
>
> R2
>
> ip multicast-routing
> interface Loopback0
> ip address 2.2.2.2 255.255.255.255
> ip pim sparse-mode
> ip ospf 1 area 0
> !
> interface Ethernet0/0
> ip address 23.0.0.2 255.255.255.0
> ip pim sparse-mode
> no ip mroute-cache
> half-duplex
> !
> interface Ethernet0/1
> ip address 123.0.0.2 255.255.255.0
> ip pim sparse-mode
> no ip mroute-cache
> half-duplex
> !
> interface Serial1/0
> ip address 12.0.0.2 255.255.255.0
> ip pim sparse-mode
> no ip mroute-cache
> serial restart-delay 0
> clock rate 64000
> router ospf 1
> log-adjacency-changes
> network 0.0.0.0 255.255.255.255 area 0
> !
> ip pim rp-address 2.2.2.2
> !
>
> R3
>
> ip multicast-routing
>
> interface Ethernet0/0
> ip address 23.0.0.3 255.255.255.0
> ip pim sparse-mode
> no ip mroute-cache
> half-duplex
> interface Ethernet0/1
> ip address 123.0.0.3 255.255.255.0
> ip pim sparse-mode
> no ip mroute-cache
> half-duplex
>
> interface Serial1/0
> ip address 13.0.0.3 255.255.255.0
> ip pim sparse-mode
> no ip mroute-cache
> serial restart-delay 0
> clock rate 64000
> router ospf 1
> log-adjacency-changes
> network 0.0.0.0 255.255.255.255 area 0
> ip pim rp-address 2.2.2.2
>
> R4
>
> ip multicast-routing
> interface Ethernet0/1
> ip address 123.0.0.4 255.255.255.0
> ip pim sparse-mode
> ip igmp join-group 239.1.1.1
> half-duplex
> router ospf 1
> log-adjacency-changes
> network 0.0.0.0 255.255.255.255 area 0
> ip pim rp-address 2.2.2.2
>
> When R1 pings the group address (streams traffic destined to the group)
> 239.1.1.1
> debug ip mpacket shows on R2,R3,R4
> R2:
> *Mar 1 00:07:43.275: IP(0): s=12.0.0.1 (Serial1/0) d=239.1.1.1
> (Ethernet0/1) id
> =1, ttl=254, prot=1, len=100(100), mforward
> *Mar 1 00:07:43.287: IP(0): s=13.0.0.1 (Ethernet0/1) d=239.1.1.1 id=1,
> ttl=253,
> prot=1, len=114(100), mroute olist null
> R3
> *Mar 1 00:07:15.467: IP(0): s=13.0.0.1 (Serial1/0) d=239.1.1.1
> (Ethernet0/1) id
> =1, ttl=254, prot=1, len=100(100), mforward
> *Mar 1 00:07:15.495: IP(0): s=12.0.0.1 (Ethernet0/1) d=239.1.1.1 id=1,
> ttl=253,
> prot=1, len=114(100), mroute olist null
> R4
> *Mar 1 00:06:16.187: IP(0): s=13.0.0.1 (Ethernet0/1) d=239.1.1.1 id=1,
> ttl=253,
> prot=1, len=114(100), mroute olist null
> *Mar 1 00:06:16.199: IP(0): s=12.0.0.1 (Ethernet0/1) d=239.1.1.1 id=1,
> ttl=253,
> prot=1, len=114(100), mroute olist null
>
> This shows that R4 is getting two packets one is being forwarded through
> R2,and the other through R3.
>
> Best Regards,
>
> On Sun, Oct 11, 2009 at 10:49 PM, Divin Mathew John <divinjohn_at_gmail.com>wrote:
>
>> its probable that after the first packet u switchover to source path
>> tree[SPT] . try with ip pim spt-thres infini
>>
>>
>> On Sun, Oct 11, 2009 at 6:10 PM, karim jamali <karim.jamali_at_gmail.com>wrote:
>>
>>> Dear Divin,
>>>
>>> I didn't get you clearly. Are you saying that both routers can forward @
>>> the same time as this is what is happening with me?
>>> Please explain more. The thing that is happening with me is that both
>>> routers (R2,R3) are forwarding multicast traffic to the presumed client
>>> (R4). However the thing is that I thought that only one forwarder will be
>>> elected on a common subnet and this router will forward multicast traffic to
>>> the subnet.
>>>
>>> Can you please explain in more detail?
>>>
>>> Thank You
>>>
>>> Best Regards,
>>> On Sun, Oct 11, 2009 at 3:08 PM, Divin Mathew John <
>>> divinjohn_at_gmail.com> wrote:
>>>
>>>> yep.
>>>>
>>>> highest is the DR. but lowest ip address needn't necessarily forward
>>>> multicast traffic onto the broadcast domain.1
>>>>
>>>> The assert election criteria are as follow in decreasing order of
>>>> priority:
>>>>
>>>> 1- administrative distance to the source S (10.10.10.1)
>>>>
>>>> 2- Cost of the route to S (10.10.10.1)
>>>>
>>>> 3- Highest multicast interface IP address.
>>>>
>>>> refer
>>>> http://cciethebeginning.wordpress.com/2008/07/16/pim-assert-message/
>>>>
>>>> On Sun, Oct 11, 2009 at 3:59 PM, karim jamali <karim.jamali_at_gmail.com
>>>> > wrote:
>>>>
>>>>> Dear Gents,
>>>>>
>>>>> I have a confusion regarding multicast. I am running a sparse-mode
>>>>> scenario
>>>>> which is shown in the attached visio file.
>>>>> R1 s1/0 -->R2 s1/0 (12.0.0.0/24)
>>>>> R1 s1/1 -->R3 s1/0 (13.0.0.0/24)
>>>>>
>>>>> R2 fa0/0-->R3 fa0/0(23.0.0.0/24)
>>>>> R2 fa0/1 -->R3 fa0/1 -->R4 fa0/1 all on the same subnet (123.0.0.0/24)
>>>>>
>>>>> Pim Sparse mode is running on all the common interfaces & neighbor
>>>>> relationship is formed. On R2, I have a loopback (2.2.2.2) which is the
>>>>> RP
>>>>> of the my network.
>>>>>
>>>>> Note that I am running OSPF everywhere.
>>>>>
>>>>> The confusion is related to the common subnet of R2,R3,R4. From what I
>>>>> understood, on every common subnet one Querier,and one Forwarder is
>>>>> elected,
>>>>> and one Designated Forwarder is Elected.As far as I understand, the
>>>>> Querier
>>>>> is the one sending queries asking if anyone wants to join a certain
>>>>> group.A
>>>>> forwarder is the one forwarding the stream to the subnet. The
>>>>> designated
>>>>> router as far as I understand is the the first layer 3 device which
>>>>> knows
>>>>> about the stream from the streamer,and sends a register message to the
>>>>> RP
>>>>> notifying it that a source exists. Please correct me if any of my
>>>>> concepts
>>>>> is wrong.
>>>>>
>>>>> The router with the lowest IP address is the querier and the one with
>>>>> the
>>>>> highest IP address is the forwarder. In the scenario I have shown, R1
>>>>> is the
>>>>> source, R2's loopback is the RP and R4 ethernet interface has joined a
>>>>> group
>>>>> (239.1.1.1). When I ping from R1, I notice that the stream on R4 is
>>>>> being
>>>>> received from both R2,and R3?Does this break the concept of forwarder?
>>>>>
>>>>> I would be grateful for any help.
>>>>>
>>>>> Best Regards,
>>>>>
>>>>> KJ
>>>>>
>>>>>
>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>
>>>>> _______________________________________________________________________
>>>>> Subscription information may be found at:
>>>>> http://www.groupstudy.com/list/CCIELab.html
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>>
>>>>
>>>> Umberto Eco <http://www.quotationspage.com/quote/320.html> - "I felt
>>>> like poisoning a monk."
>>>>
>>>
>>>
>>>
>>> --
>>> KJ
>>>
>>
>>
>>
>> --
>>
>> Sent from Karnataka, India
>> Umberto Eco <http://www.quotationspage.com/quote/320.html> - "I felt
>> like poisoning a monk."
>>
>
>
>
> --
> KJ
>

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