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First of all, may I welcome you to my site. My name is Chris and I'm from the UK and work as a Systems Engineer for Cisco. This blog was initially created to post up my subnetting technique but has now got more stuff to do with attaining Cisco certifications. Either way I really hope that the content is sufficent for your needs and I look forward to hearing your feedback. If you find that the content really helps you please feel free to donate using the PayPal link on the right.

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OSPF and NBMA Networks

Confused about which NBMA network type requires a DR/BDR or neighbours to be statically defined? Worry no longer..............................

If the keyword nonbroadcast is within the network type (i.e. ip ospf network non-broadcast, or ip ospf network point-to-multipoint non-broadcast) then neighbours must be defined.

If the keyword point is within the network type (i.e. ip ospf network point-to-point, ip ospf network point-to-multipoint, ip ospf network point-to-multipoint non-broadcast) then a DR/BDR is NOT elected.

You may see a question which has an output showing the network type as point-to-multipoint. It will then ask you to choose a couple of correct answers. From above we know the answer to be that DR/BDR are not elected and neighbours do not need to be statically defined.

HTH!

Posted byChris Bloomfield at 15:47  

2 comments:

Peter said... 22 October 2008 at 01:37  

Chris,

in both cases where you determine if a DR/BDR is NOT elected or neighbourz must be defined you have the example:

ip ospf network point-to-multipoint non-broadcast

Is there a typo anywhere?

Peter

Vijay Bhosale said... 3 February 2013 at 16:57  

Hi, can you help me with this;
Determine the summary address and the mask to be used that will summarize the subnet 172.148.0.0/13 through 172.156.0.0/13
Explanations will be appreciated.
Thanks

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