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New Member

OSPF network

Which type of OSPF network requires manual configuration of OSPF neighbors?

A. broadcast multi-access

B. nonbroadcast multi-access

C. point-to-point

D. point-to-multipoint

regards

Neo

8 REPLIES

Re: OSPF network

you have to manually configure the neighbors in point to multipoing nonbroadcast ...

rate this post if it helps

regards

Devang

New Member

Re: OSPF network

and on NBMA ??

regards

Neo

Re: OSPF network

see:

broadcast: uses multicast hello and automatically discover neighbour...

NBMA: neighbour must be manually configured

Point to multipoint: multicast hello and automatically discover neighbor...

point to multipoint non broadcast: neighbors must be manually configured

hope you get your all answers

rate this post if it helps

regards

Devang

New Member

Re: OSPF network

That means answer to above question is NBMA not point-to-multi point.

regards

Neo

Re: OSPF network

Hi,

That's correct. NBMA is the correct answer.

Here's an apt explanation from CCO for it:

In an NBMA network topology, which is inherently nonbroadcast, neighbors are not discovered automatically. OSPF tries to elect a DR and a BDR due to the multi-access nature of the network, but the election fails since neighbors are not discovered. Neighbors must be configured manually to overcome these problems. Also, additional configuration is necessary in a hub and spoke topology to make sure that the hub routers, which have connectivity with every other spoke router, are elected as the DR and BDR. Alternatively, you can change the configuration on the NBMA interface to make OSPF believe that it is another network type that does not have these problems.

Hope that helps!

Regards,

Sundar

New Member

Re: OSPF network

great!i ahev 2 questions

1)I am im impression that hub and spkoe is same as NBMA tech

2) and how can i change the configuration on NBMA ?

regards

Neo

New Member

Re: OSPF network

any help !!!

Re: OSPF network

NBMA (non-broadcast multiple access) is one of four network types in the OSPF (Open Shortest Path First) communications protocol. NBMA is used to accurately model X.25 and frame relay environments in multiple-access networks where there are no intrinsic broadcast and multicast capabilities. The other OSPF network types are: broadcast, point-to-point, and point-to-multipoint. In an NBMA configuration, OSPF sends HELLO packets (packets sent periodically to establish and confirm neighbor relationships between routers) to each router one at a time rather than multicasting them. The HELLO timer (which tells the router how often to send HELLO packets) is extended from 10 to 30 seconds and the dead router timer (which tells the router how long to wait before it decides that a neighboring router is not functioning) is extended from 40 to 120 seconds...yes you can have HUB and SPOKE as NBMA in fact frame relay is same...

hope this helps you

rate all the helpful post

regards

Devang

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