From: Jian Gu (guxiaojian@gmail.com)
Date: Fri Jun 16 2006 - 04:33:49 ART
On 6/15/06, kasturi cisco <kasturi_cisco@hotmail.com> wrote:
>
> Hello,
>
> Here is how i look at it. The Are-filter list is for filtering the ABR
> Type
> 3 link-state advertisement (LSA). This Filtering feature extends the
> capability of an ABR that is running the OSPF protocol to filter type 3
> LSAs
> between different OSPF areas. This feature allows only specified prefixes
> to
> be sent from one area to another area and restricts all other prefixes.
> This
> type of area filtering can be applied out of a specific OSPF area, into a
> specific OSPF area, or into and out of the same OSPF areas at the same
> time.
>
> >I tried filtering External LSA's between areas with an area filter list
> but
> > >it does not work! I was told that filter lists do not work on External
> >LSA's. Is that true? >
>
> To filter External LSA some mechanisms that may be used are: Stub areas,
> Totally stubby (filters external+inter-area also) or with
> route-summarization with "not-advertise". Wont this work ? Depends on the
> scenario u have.
>
> >Also I tried using inbound distribute lists but it seems the External
> LSA's
> >are still being forwarded to the next hop routers and it seems I have to
> >use
> >distribute lists on all the routers... > >How do you filter External
> LSA's?
>
> I dont think ditribute-list is an option for OSPF which is a link state
> protocol. This is normal behaviour. To filter routes in OSPF we would need
> to use this on evey router bcoz the LSA will still get flooded as the OSPF
> database have to be similiar across all OSPF areas per link state std. So
> route-filtering using distribute list is ONLY an option for DV protocols.
how do you think about the following link:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hirp_c/
ch15/hroutma.htm
HTH.
> Kasturi.
>
>
>
> >From: CCIEin2006 <ciscocciein2006@gmail.com>
> >Reply-To: CCIEin2006 <ciscocciein2006@gmail.com>
> >To: "Cisco certification" <ccielab@groupstudy.com>
> >Subject: Not possible to filter External LSA's between areas in OSPF?
> >Date: Thu, 15 Jun 2006 11:21:10 -0400
> >
> >Hello group,
> >
> >I tried filtering External LSA's between areas with an area filter list
> but
> >it does not work! I was told that filter lists do not work on External
> >LSA's. Is that true?
> >
> >Also I tried using inbound distribute lists but it seems the External
> LSA's
> >are still being forwarded to the next hop routers and it seems I have to
> >use
> >distribute lists on all the routers...
> >
> >How do you filter External LSA's?
> >
> >Thanks.
> >
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