OSPF Router id

Unanswered Question
Mar 26th, 2007
User Badges:

Hi,


Iam doing my CCNP BSCI and i had a small confusion on the DR and BDR selection and i want to know how they are selected.

Can u help me in short points How ospf process election is done in NBMA,PPP,Point to multipoint


Thanks in Advance

Vinoth







  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 3 (1 ratings)
Loading.
achalante Tue, 03/27/2007 - 04:27
User Badges:

It's quite simple. You must understand that there is no DR/BDR election in ppp and ppmp modes. It only occurs in Broadcast and NBMA modes. Apparently, it bases it's selection a couple of things, but the most important is the priority. The router with the highest priority would be elected as the DR, while the router with the higher priority remains the BDR. Should there be a DR failure, the BDR takes the place of a DR, even after the former DR comes back online, the new DR still remains the DR. In a sense, the DR election works in a round-robin fashion, in that you'd need to clear the ospf processes until the original DR finally becomes the DR again. I hope this helps.

vinoth.kumar Tue, 03/27/2007 - 05:20
User Badges:

Hi,


Thanks to you for replying me, my comment is what are all the factor that involves in DR and BDR election

Like Higher loopback address


Regards

vinoth

Jon Marshall Tue, 03/27/2007 - 05:34
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

Hi Vinoth


Each interface on a router that is part of a multiaccess network has a router priority in OSPF. If the priority is 0 that router cannot become a DR or BDR for that network segment.


When a router becomes active, once it has discovered it's neighbours it then checks to see if there is a DR and BDR. If there isn;t a BDR an election is held. if there isn't an active DR the BDR gets promoted and another election is held for the BDR.


In the event of a tie in terms of router priority the router with the highest router ID wins.


HTH


Jon

cpembleton Tue, 03/27/2007 - 05:40
User Badges:
  • Silver, 250 points or more

Just to add:


Router ID is the hightes loopback address. If no loopback address is set the the highest active interface is used.


Set a loopback! The highest active interface can change if an interface goes down.


Thanks,

Chad


vinoth.kumar Mon, 04/02/2007 - 23:53
User Badges:

Thanks for reply


I had got a router 3845and 3725 and i want to run a BGP protocol on the 3845 router but when i try to enter #router bgp AS number it is showing protocol not matched for this image (my IOS version is 12.3 (11))


I need your help in this to configure my BGP protocol and which version will support for this


Thanx in Advance

Vinoth



vinoth.kumar Tue, 04/03/2007 - 03:53
User Badges:

what is the ios version and image i have to install


Regards

Vinoth

achalante Tue, 04/03/2007 - 03:58
User Badges:

this would work: c3845-advipservicesk9-mz 12.4(2)T

vinoth.kumar Tue, 04/17/2007 - 01:32
User Badges:

Hi


I want to know that which routing protocol will support for multi brand routers


Thanks in Advance

vinoth

c.lemaire Tue, 04/17/2007 - 03:23
User Badges:

All standardized protocols should work. OSFP, BGP, RIP, IS-IS

vinoth.kumar Tue, 05/08/2007 - 02:56
User Badges:

Hi,


I need information that when i configuring the ospf authentication as example


#area 2 authentication

#interface serial 0

#ip ospf message digest-key ? when i use IOS help

it is showing 0 7

what it means of range choosing the option


And the second information is while enabling the debug to see the OSPF adjcency after configuring the OSPF authentication (md5)it is showing as

#debug ip ospf adj


it is showing some line as


send me the youngest key- what it means


can u help me in getting the both information


Thanks in advance

Vinoth


mohammedmahmoud Tue, 05/08/2007 - 03:11
User Badges:
  • Green, 3000 points or more

hi,


0 for not yet encrypted, 7 for proprietary encrypted (using the weak reversible algorithm - needs service password-encryption enabled).


And the reason for this error is most probably that you didn't add the " ip ospf message-digest-key" command under the interface properly.


HTH, please rate all helpful posts,

Mohammed Mahmoud.

vinoth.kumar Tue, 05/08/2007 - 03:17
User Badges:

Hi,


Thanks fo your prompt reply


from that 0 - for not yet encrypted (what it defines )if enabled with 0 what will be the result


7 - what will be the result


please do the needfull


Regards

vinoth

mohammedmahmoud Tue, 05/08/2007 - 03:27
User Badges:
  • Green, 3000 points or more

hi,


If you are going to add the OSPF password (key) in plain text use 0, and if you are going to enter it in the encrypted form use 7.



HTH, please do rate helpful posts,

Mohammed Mahmoud.

Actions

This Discussion