From: Arun Arumuganainar (aarumuga@hotmail.com)
Date: Tue Jul 19 2005 - 13:02:52 GMT-3
For choosing the right ospf network types . Let me summarize it this way .
1) Find out what is network topology : Your topology could be Full mesh or
Partial mesh ( include Hubs and spoke also to partial mesh group )
2) If its Full Mesh : All ospf network types will work . This includes . a)
NBMA ( Default ) ,b) BMA ( ip ospf network broadcast ) ,C) P2MP , D) P2MP
Non-broadcast , and E) P2P
3) For A and D : Use Neighbor Statements . For A and B : Influence DR
election ( configure ospf priority for Neighbors or on the interface )
Note : For P2MP( Both broadcast and Non Broadcast ) and P2P case DR election
will not happen .
4 )For Partial Mesh : Use only P2P or P2MP ( both Broadcast and Non
broadcast modes can be used ) .You will have manually configure neighbor in
case of P2MP.
With the above 4 point you will be able to arrive at correct ospf network
type base on the topology and also the constraints given in the question
sheet .
Hope this helps
Thanks and Regards
Arun
----- Original Message -----
From: "Chris Lewis (chrlewis)" <chrlewis@cisco.com>
To: "Brian Lee" <ipgirl@gmail.com>; <ccielab@groupstudy.com>
Sent: Tuesday, July 19, 2005 8:17 PM
Subject: RE: Re: Ospf network types
> Just to add some detail to what others have already said.
>
> One of the reasons P2mp non-broadcast came in to being was because lots
> of TAC cases were created by people forgetting to put in the broadcast
> keyword on the frame map statements. So p2mp non-broadcast is a way to
> get p2mp to work with the neighbor command, making the broadcast
> keyword on the map statement not necessary. In the exam this is used if
> you are told not to use the broadcast keyword on the map statements.
> Consider the following
>
> R1:
> interface Serial2/0
> ip address 10.1.1.1 255.255.255.0
> encapsulation frame-relay
> ip ospf network point-to-multipoint
> no fair-queue
> frame-relay map ip 10.1.1.2 122
> no frame-relay inverse-arp
> !
> router ospf 1
> log-adjacency-changes
> network 10.1.1.1 0.0.0.0 area 0
> neighbor 10.1.1.2 cost 100
>
> R2:
> interface Serial1/0
> ip address 10.1.1.2 255.255.255.0
> encapsulation frame-relay
> ip ospf network point-to-multipoint
> no fair-queue
> frame-relay map ip 10.1.1.1 221
> no frame-relay inverse-arp
> !
> router ospf 1
> log-adjacency-changes
> network 10.1.1.2 0.0.0.0 area 0
> neighbor 10.1.1.1 cost 100
>
> R1 and R2 can ping each other's 10.0.0.0 interfaces, the network type is
> p2mp and there is a neighbor statement, however the neighbors do not
> form, as each router is still trying to send to the multicast address
> with this network type, which leads to an encapsulation failed error
> when the router tries to ship the packet over the frame link. To get
> this setup to work, all you need do is change the network type to p2mp
> non-broadcast, the neighbor statement takes effect, R1 and R2 start
> sending unicast OSPF packets and neighbors form.
>
> Chris
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Brian Lee
> Sent: Monday, July 18, 2005 10:56 AM
> To: ccielab@groupstudy.com
> Subject: Re: Re: Ospf network types
>
> hi,
> I have the same question, could anyone gives us an explanation ?
>
> Thanks
>
> Lee.
>
> ----- Original Message -----
> From: "Sharma, Mohit" <mohit.sharma@hp.com>
> To: <ccielab@groupstudy.com>
> Sent: Sunday, June 20, 2004 10:36 PM
> Subject: Ospf network types
>
>
> > HI All,
> >
> > Could somebody please explain the difference between using ospf
> network
> > type point-to-multipoint and point-to-multipoint nonbroadcast.
> >
> > The only difference I could read on the doc cd's was that with the
> added
> > nonbroadcast option you can use neighbor statement and assign costs to
> > the neighbor spokes to distinguish between more or less preferred
> links.
> >
> > But I did the same thing with just using the p2m option without using
> > nonbroadcast and was able to assign the cost to the spokes.
> > Then why do we need the nonbroadcast????
> >
> > Also another question-IF ospf should send ONLY unicast messages to the
> > neighbor, then the only option would be to use nbma with neighbor
> > command or is there any other option available which is send unicast??
> >
> > Thanx,
> > Mohit.
> >
> >
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