Hi Acee,


I used distribution list to drop the routing update packet (coming from DR)
only with this destination address “*ALLSPFRouters*” at Backup designated
router and

BDR received (without dropping) a routing update packet with destination
address *ALLDRouters*



And I checked the routing table; Expected route is not installed in routing
table that means BDR couldn’t process the update packet with destination
address as “*ALLDRouters*”



Regards,

*Thirumavalavan *

Consultant

[image: Description: Description: Description: IP
Infustion]<http://www.ipinfusion.com/index.html>



*From:* Acee Lindem [mailto:[email protected]]
*Sent:* Tuesday, December 27, 2011 11:54 PM
*To:* Thirumavalavan Periyannan
*Cc:* <[email protected]>
*Subject:* Re: [OSPF] Clarification of DR & BDR Processing in OSPFV3



Hi Thirumalvalavan,

See inline.

On Dec 27, 2011, at 6:46 AM, Thirumavalavan Periyannan wrote:



Hi All,



I have a doubt in DR and BDR process in OSPFV3.



“   *AllDRouters*:

                     This multicast address has been assigned the value
FF02::6.

   *Both the Designated Router and Backup Designated Router must be*

*   prepared to receive packets* destined to this address.  Certain

   OSPF protocol packets are sent to this address during the

   flooding procedure.”



RFC says, DR & BDR must be *prepared* to receive packets destined to
FF02::6, Here is that *Prepared* means to say BDR needs

to process the packet with destination address FF02::6 (ALLDRouters)?



Yes. This is somewhat implementation and network interface type specific
but it implies that the packet will be received and passed to the OSPFv3
instance's receive queue.

For example, on ethernet this implies that packets sent the Multicast MAC
33:33:00:00:00:06.





In CISCO routers, BDR is not processing the packet with destination address
“ALLDRouters”.

But the same BDR when it receives an update packet with destination address
as “ALLSPFRouters”, it is processing the packet.



The receiving OSPFv3 router should process all packets addressed to
FF02::6. I'd advise you turn on some debugs on the both the sending and
receiving OSPFv3 routers to determine whether or not the packet is being
rejected.



Hope this helps,

Acee





So I want a clarification of the above lines in the standard.



Regards,

*Thirumavalavan*

Consultant

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