Shivi,
my understanding is that the distribute list controls which routes are
injected from the OSPF routing table in the overall routing table.
OSPF is a "Link-State-Protocol", all OSPF routing tables within an
area are identical. You can find some more information about that
issue and OSPF in general at http://www.cisco.com/warp/public/104/1.html
We use the distribute lists to suppress the default route (which is
present in OSPF) on interconnections routers.
Steffen Baur
On Mon, Nov 22, 1999 at 12:41:25AM -0500, Shivi Fotedar wrote:
> I'm interested in how Cisco's "distribute in" command
> works in OSPF context. It seems that if you specify
> the access list and the interface name in OSPF
> context, then it lets the LSAs arriving over the
> specified interface into the OSPF database (that is,
> it doesn't drop them since the database of two
> neighbors have to be synchronized), but drops the
> routes resulting from those LSAs if the access list
> denies such routes.
> My first question is does Cisco drop the routes
> depending on which interface the LSAs arrived on, or
> does it drop the routes if the routes have the same
> forwarding interface as the one specifed in the
> distribute in command?
> My second question is what is the purpose of this
> command in OSPF context? It might lead to black holes,
> since this router may flood the LSAs to another
> neighbor which may install the routes. Now, the
> upstream router will forward packets destined for such
> routes to the given router which will simply drop
> them. ISIS doesn't support this command and it seems
> that OSPF also shouldn't do it. What was the reason
> for implementing this command?
>
> Shivi Fotedar
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