There is nothing to disable since split horizon does not apply to OSPF. There is a split horizon like behavior in regards to OSPF loop prevention mechanism in regards to LSA 3 not being propagated back into Area 0 as previously mentioned, but thats about it. Correct answer to the OEQ would be something in those lines, after all Cisco has not said that there are going to be “yes” only questions on the test.
Stan On 8/17/09 11:50 AM, "Devang Patel" <[email protected]> wrote: > Yes... OSPF with in area is link state but between area it behave like > Distance Vector Protocol... > > On Mon, Aug 17, 2009 at 12:44 PM, Steve Shaw <[email protected]> wrote: >> To elaborate on Kim's answer: >> >> OSPF Area Border Routers act much like routers running a distance vector >> protocol when it comes to type-3 LSAs from other OSPF areas. >> 1. An ABR will never re-advertise a learned type-3 LSA back into area 0 >> (split-horizon) >> 2. ABRs ignore LSAs created by other ABRs when learned through a non-backbone >> area. >>> * Prevents an ABR from choosing a non-backbone path to area 0 >> >> These rules can be overcome by a virtual link between ABRs in the event of a >> backbone area partition. >> >> On Mon, Aug 17, 2009 at 2:06 PM, Kim Pedersen <[email protected]> wrote: >>> Hi, >>> >>> The only "split-horizon"- like thing i can come up with consists of >>> ABR's not propagating any information learned from a LSA type 3 from >>> another ABR through a non-backbone area, back into the backbone (area 0) >>> again. In this manner i guess you could say "dont advertise back into >>> area 0 something the area learned from area 0 in the first place". >>> >>> Dont know if thats what you are referring to. >>> >>> Sincerely, >>> Kim Pedersen >>> >>> desmond Black wrote: >>>> > >>>> > Explanation given is to mean that there is no Split-Horizon Rule in OSPF. >>>> > >>>> > I dont want to confuse, but there is a Split-Horizon equivalent logic >>>> > of Distance-Vector R'tng Protocol in OSPF but cannot be termed >>>> > explicitly as Split-horizon. >>>> > In this logic if the Next-Hop of the Prefix is in the Area to which >>>> > the ABR is going to advertise the route [in form of LSA] OR the Prefix >>>> > itself is in that LSA...... do not advertise it into that Area. >>>> > >>>> > Desmond Black, >>>> > In Pursuit of CCIE!! >>>> > India >>>> > >>>> > ----- Original Message ----- >>>> > From: [email protected] >>>> > To: "desmond Black" >>>> > Cc: ��ս�� , [email protected] >>>> > Subject: Re: [OSL | CCIE_RS] How to disable OSPF splite horizon ? >>>> > Date: Mon, 17 Aug 2009 16:25:14 +0000 (GMT) >>>> > >>>> > can you give a bit more detail on the ospf split horizon pls... >>>> > >>>> > ----- Original Message ----- >>>> > From: desmond Black >>>> > Date: Monday, August 17, 2009 10:28 am >>>> > Subject: Re: [OSL | CCIE_RS] How to disable OSPF splite horizon ? >>>> > To: 邵战新 , [email protected] >>>> > >>>> > > Split-Horizon is needed in Distance vector Protocols since they >>>> > > do not >>>> > > have complete view of the topology and therefore to avoid loops >>>> > > tehy do >>>> > > not send back the routes originated by advertising peer back to >>>> > > it. RIP >>>> > > actually uses Split-horizon with Poison-Reverse just for making >>>> > > it sure. >>>> > > Since Protocols like OSPF & ISIS do have complete view of the >>>> > network >>>> > > they can make the decision themselves when the routes advertised >>>> > > by them >>>> > > will have had covered most "COST" and therefore would never get >>>> into >>>> > > Routing table. >>>> > > >>>> > > ----- Original Message ----- >>>> > > From: 邵战新 >>>> > > To: [email protected] >>>> > > Subject: [OSL | CCIE_RS] How to disable OSPF splite horizon ? >>>> > > Date: Mon, 17 Aug 2009 19:12:07 +0800 >>>> > > >>>> > > I got this open end question in ccie lab exam. Although I >>>> > > search it , >>>> > > I can't get answer. Who can know it ? Thanks >>>> > > >>>> > > --------------------------------------------------------------- >>>> > > ----- >>>> > > >>>> > > 搜索本应是快乐的，不是么? 快乐搜索，有问必应！微软隆重推出! >>>> > > 立即试用！ >>>> > > _______________________________________________ >>>> > > For more information regarding industry leading CCIE Lab training, >>>> > > please visit www.ipexpert.com <http://www.ipexpert.com> >>>> > > >>>> > > >>>> > > >>>> > > >>>> > > Desmond Black, >>>> > > In Pursuit of CCIE!! >>>> > > India >>>> > > >>>> > > -- >>>> > > Be Yourself @ mail.com <http://mail.com> ! >>>> > > Choose From 200+ Email Addresses >>>> > > Get a Free Account at www.mail.com <http://www.mail.com> ! >>>> > > >>>> > > >>>> > >>>> > >>>> > >>>> > >>>> > >>>> > -- >>>> > Be Yourself @ mail.com <http://mail.com> >>>> > Choose From 200+ Email Addresses >>>> > Get a *Free* Account at www.mail.com <http://www.mail.com> >>>> <http://www.mail.com>! >>>> > ------------------------------------------------------------------------ >>>> > >>>> > _______________________________________________ >>>> > For more information regarding industry leading CCIE Lab training, please >>>> visit www.ipexpert.com <http://www.ipexpert.com> >>>> > >>> >>> -- >>> >>> // Freedom Matters >>> // Follow my progress on: http://kpjungle.wordpress.com >>> >>> _______________________________________________ >>> For more information regarding industry leading CCIE Lab training, please >>> visit www.ipexpert.com <http://www.ipexpert.com> >> >> >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com <http://www.ipexpert.com> >> > > > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com
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