From: subodh.rawat@wipro.com
Date: Wed Nov 14 2007 - 09:23:00 ART
That's right. Lab it up if you have doubt.
Best way is to see "show ip ospf interface command" output this will
give you complete picture.
HTH
Subodh
-----Original Message-----
From: Gary Duncanson [mailto:gary.duncanson@googlemail.com]
Sent: Wednesday, November 14, 2007 5:50 PM
To: Subodh Singh Rawat (WT01 - TELECOM SERVICE PROVIDER)
Cc: ananth.vk@tcs.com; ccielab@groupstudy.com
Subject: Re: OSPF Network Query Clarification
Yes it was discussed recently wasn't it. In fact it's been discussed
many times over the years in archives.
IMHO one of the best way's to understand all this is to do the reading,
lab up the alternatives and watch the debugs. Understanding why things
work the way they do and why you need to know all this instead of trying
to remember the differences in a list.
Rgds
Gary
----- Original Message -----
From: <subodh.rawat@wipro.com>
To: <ananth.vk@tcs.com>; <ccielab@groupstudy.com>
Sent: Wednesday, November 14, 2007 11:20 AM
Subject: RE: OSPF Network Query Clarification
>I hope its not going to start again an endless debate on 5+4+3+2+1
> theory.
>
> Anand,
> You can serach last month archive, this was discussed in Oct.
>
> HTH
> Subodh
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Ananth Vk
> Sent: Wednesday, November 14, 2007 3:20 PM
> To: ccielab@groupstudy.com
> Subject: OSPF Network Query Clarification
>
> Hi Everyone,
>
> Good Morning !
>
> Was going thru ospf nwk types in Jeff Doyle, cisco site & netcraftsmen
&
> have a few clarifications..
> ok, My understanding of network types...There are 5 of them
>
> 1. Point to Point (Serial / PPP/HDLC)
> 2. Broadcast (Ethernet, Token ring)
> 3. Point to Multipoint Nonbroadcast-NBMA- (FR, ATM) (partial mesh,
> neighbour cnds need to be added) 4. Point to Multipoint Broadcast (FR,
> ATM), (For full mesh, no neighbor setup needed) 5. Virtual Links (B/w
> two ABRs to connect partitioned area / to connect an area that dont
have
> direct area 0 connectivity)
>
>
> My understanding, pls correct if im wrong
>
> 1. Is DR election mandatory for all the 5 network types ? only for
2,3,4
> i guess.
> 2. OSPF updates are sent in the form of unicast for 1 & 5, broadcast
for
> 2,4 and multicast (only when selective routers need to recv updates)
for
> 3
>
> 3. Neighbour command is mandatory only for 3 4. FR if im right will
fit
> with 3 (partial mesh) & 2,4 (full mesh)....can any other type be used
> with FR ?
>
>
------------------------------------------------------------------------
> -----
> -----------------------
> From
http://www.cisco.com/en/US/docs/ios/11_3/feature/guide/ospfpmp.html
>
> OSPF has two new features related to point-to-multipoint networks. One
> feature applies to broadcast networks; the other feature applies to
>
> nonbroadcast networks.
>
> ?On point-to-multipoint, broadcast networks, there is no need to
specify
> neighbors. However, you can specify neighbors with the neighbor
command,
>
> in which case you should specify a cost to that neighbor.
>
> ?On point to multipoint, nonbroadcast networks, you now use the
neighbor
> command to identify neighbors. Assigning a cost to a neighbor is
> optional.
>
>
------------------------------------------------------------------------
> -----
> -----------------------
> From http://www.netcraftsmen.net/welcher/papers/ospf3.htm
>
> You can configure an interface as any type you wish.
> Broadcast is typically used on networks where broadcast and multicast
> are supported. The idea is to send out one OSPF multicast that reaches
>
> multiple receivers. This can be appropriate with X.25 and Frame Relay
if
> you have a full mesh of PVC's. Loss of a PVC can cause problems with
> OSPF
>
> broadcast networks, however, since some routers with a common subnet
> will no longer be able to transmit directly to each other.
>
> Non-broadcast is used where broadcast/multicast is not feasible. The
> drawback to this interface type is that neighbors must be explicitly
> configured,
>
> which can get to be a nuisance.
>
------------------------------------------------------------------------
> -----
> -----------------------
>
> Thanks
> Ananth
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