Re: point to point and multipoint OSPF interfaces

From: Elias Chari (elias.chari@gmail.com)
Date: Sun Mar 04 2007 - 21:21:14 ART

Danny,

Don't make any assumptions about the lab. Learn the ospf network types
inside out and practice them all.

Ask yourself the following questions:
1. Which are compatible network types?
2. Which of them require a DR election?
3. Which ones modify the next hop?
4. Which ones use multicast vs unicast hellos?
5. What if the are restrictions on the configuration of the frame-relay
network. Do you know how to select the correct ospf network type to ensure
full reachability?

It is more likely than not that you will have specific
directions/restrictions which will lead to a certain network type. Picking
the correct network type should be second nature by the time you get to the
lab. 

--
Regards,
Elias
CCIE#17354

On 3/4/07, Darby Weaver <darbyweaver@yahoo.com > wrote:
>
> Just remember a few things - OSPF Network Types should
> be compatible.
>
> ie. P2P and P2M are compatible
> Br and NBMA are compatible
>
> Remember which ones have DR elections and which ones
> do not.
>
> Use of priority to influence this is common -  an
> interface with "ip ospf priority 0" will never try to
> win the election and become DR.  One with 255 will
> always win (unless you do it on two - but why?).
>
> Hmmm...
>
> You can set the ip ospf network type but do not always
> need to - what if you are told you cannot do this -
> remember they will likely take something away before
> they ever give it...
>
> Keep these things in mind...
>
> Always ask yourself:
>
> Is it a P2P interface?
>
> Is it a Multipoint (or logical subinterface)
> interface?
>
> Is is a Brodcast interface?
>
> Off the top...
>
>
> --- Danny Cox <dandermanuk@gmail.com > wrote:
>
> > hi folks
> >   typically in my labs, when I've been building a
> > hub&spoke setup,
> > I've configured the hub to me a point-to-mutilpoint
> > ospf network type,
> > left the spokes as point to point, and tweaked the
> > hello/dead timers
> > to make sure it works.
> >
> >   It was suggested to me recently that this was a
> > bad idea and that
> > there have been problems, unspecified, with this
> > setup.  I've yet to
> > see anything to confirm this. Assuming the lab
> > doesn't insist upon
> > using one or the other, I'd be inclined to do what
> > I've said.  Anyone
> > got reasons why I shouldn't?
> >
> > cheers
> > Danny
> >
> >
> _______________________________________________________________________
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> >
>
>
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