OSPF uses split-horizon? I don't think this is correct. I hate to be quick
to reply but there is no reason for OSPF to use split horizon. OSPF sends
updates to all adjacent neighbors, and in NBMA , and Broadcast network types
the DR forwards the updates on.
Split-horizon is used to keep routing loops from happening for a
Distance-vector protocol not a link state protocol.
There is an issue split-horizon presents when using a distance-vector
protocol in a frame-relay hub spoke topology. As you can imagine (if you
know how a distance-vector protocol diseminates updates) the hub will need
to send the update back out of the interface it received it on so that the
other spokes will receive the update. This will not be allowed to happen if
split-horizon is enabled. The spokes will not be an issue.
By default:
Physical interface frame-relay setup split-horizon will be disabled.
Subinterface frame-relay setup split-horizon will be enabled.
Also keep in mind you cannot disable split-horizon on IPX RIP.
Summation when you have a hub spoke frame-relay topology and you are using a
distance-vector routing protocol you need to disable split-horizon on the
hub. (which does leave you secceptible to the issue split-horizon was
designed to fix)
Or use a link-state protocol.
Or you could setup point-to-point subinterfaces on the hub for each spoke.
>>>Brian
>From: "Maness, Drew" <[EMAIL PROTECTED]>
>Reply-To: "Maness, Drew" <[EMAIL PROTECTED]>
>To: "'Z'" <[EMAIL PROTECTED]>, Brian <[EMAIL PROTECTED]>,
>[EMAIL PROTECTED]
>Subject: RE: FR + Poison Reverse...
>Date: Tue, 27 Feb 2001 08:36:57 -0800
>
>OSPF does use Split horizon. I don't think OSPF uses PR because PR sets
>the
>route to infinity and I'm not sure what an ' infinity' cost would mean in
>OSPF.
>
>-----Original Message-----
>From: Z [mailto:[EMAIL PROTECTED]]
>Sent: Tuesday, February 27, 2001 12:47 AM
>To: Brian; [EMAIL PROTECTED]
>Subject: Re: FR + Poison Reverse...
>
>
>But I thought that I'd seen or heard of using split horizon with
>OSPF...maybe I'm thinking of Frame Relay...long day I guess...
>
>************************************************************
>This has been an Eyez Only streaming e-mail broadcast...We are watching.
>
>NetEyez ~ CCNP, CCDA
>
>----- Original Message -----
>From: "Brian" <[EMAIL PROTECTED]>
>To: "Z" <[EMAIL PROTECTED]>
>Cc: <[EMAIL PROTECTED]>
>Sent: Tuesday, February 27, 2001 1:16 AM
>Subject: Re: FR + Poison Reverse...
>
>
> >
> >
> > split horizon and PR are both associated with distance vector protocols,
> > OSPF is a link state protocol.
> >
> > Brian
> > On Mon, 26 Feb 2001, Z wrote:
> >
> > > Hey Group,
> > > I recently pondered something while at work and nobody could give
>me
>a
> > > strait answer. Actually I feel a little embarrassed asking this due to
>me
> > > being an NP and I feel like I should know this. Guess this type of
>thing
> > > doesn't come up much around me. Question is: Can poison reverse (PR)
>be
>used
> > > with OSPF? I know split horizon is used with it but I just cant see
>why/how
> > > poison reverse would. My definition of PR is that it sets the link to
>the
> > > max hop count and deems it unreachable, hence the term poison. I can't
>see
> > > how this would work with OSPF because it doesn't use a hop count.
>Maybe
>I'm
> > > confused about PR. Does it set the link to the highest metric, and not
>hop
> > > count? Maybe I'm just used to hearing about PR in discussions of RIP
>that
> > > I'm assuming it set the hop count to the highest and has nothing to do
>with
> > > metric. Any clarity would help, thanks all...
> > >
> > > ...sorry for the rambling...
> > >
> > > ************************************************************
> > > This has been an Eyez Only streaming e-mail broadcast...We are
>watching.
> > >
> > > NetEyez ~ CCNP, CCDA
> > >
> > >
> > >
> > > _________________________________
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> >
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> >
> > Brian Feeny,CCDP,CCNP+VAS Scarlett Parria
> > [EMAIL PROTECTED] [EMAIL PROTECTED]
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> >
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> >
> >
>
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