From: Michael Davis (miked@xxxxxxxxxx)
Date: Fri Feb 15 2002 - 13:32:19 GMT-3
See inline...
> Mike:
>
> I like the condition you added, which is "routes eligible for the RIB". I
> think, you mean another routing source, which has lower adminstrative
> distance, didn't inject the same route into routing table.
I'm not sure what you're saying here.
>
> For ospf, when you say the routing bit set, do you mean the routes
resulted
> from SPF, and also in the RIB? In other words, any route which does not
> exist in the routing table will not be redistributed?
Yes and No. Yes, they resulted from SPF calculations. No, they might not
also be in the RIB. There's a difference between what is "RIB eligible" (for
want of a better expression) and what actually makes it to the RIB.
Consider the following:
interface loopback 0
ip address 192.168.1.0 255.255.255.0
!
router rip
network 192.168.1.0
!
router eigrp 1
network 192.168.1.0
!
router ospf 1
network 192.168.1.0 0.0.0.255 area 0
When we look at the RIB (sh ip route,) we see that because routes sourced
from connected interfaces have the lowest AD, only they actually make it to
the RIB.
But each of the routing protocols will contain 192.168.1.0/24 as a valid
route that _could_ be chosen for the RIB even though in this case it wasn't
actually placed in the RIB. And thus, 192.168.1.0/24 is redistributable by
all of these processes.
Mike
>
> Thanks for the input
>
> james
>
>
> -----Original Message-----
> From: Michael Davis [mailto:miked@netrus.net]
> Sent: Thursday, February 14, 2002 5:21 PM
> To: Xu, James; 'Lab Candidate'; ccielab@groupstudy.com
> Subject: Re: How route redistribution EXACTLY works --- need
> confirmation
>
>
> Hi James,
>
> >From my experience, I agree with you.
>
> The RIP redistributes _valid_ routes from it's database. That is, routes
> learned via other rip speakers, other routing processes via
redistribution,
> connected networks covered in network statements, etc, that the RIP
process
> has not discarded and are eligible for the RIB. When you apply route-maps,
> you control which of these routes are redistributed.
>
> The same goes for OSPF. LSAs for all the area's links and routers reside
in
> the database, but not all database entries are in fact redistributed. RIP
> wouldn't know how to handle them since it doesn't do SPF. Only those with
> the routing bit set (processed by SPF and eligible for the RIB) are
> available for redistribution.
>
> Mike
>
> ----- Original Message -----
> From: "Xu, James" <james.xu@eds.com>
> To: "'Lab Candidate'" <labccie@yahoo.com>; <ccielab@groupstudy.com>
> Sent: Thursday, February 14, 2002 2:13 PM
> Subject: RE: How route redistribution EXACTLY works --- need confirmation
>
>
> > I would like add a little more to explain why I believe the RIP is not
> > picking up routes from routing table:
> >
> > Suppose there is a connected route in the router, which is configured to
> be
> > under RIP process. In the routing table, this route will be showed as
> > "connected". But the RIP still is redistributing this route out anyway.
> As
> > a fact, this route shows up on your rip database too.
> >
> > James
> >
> > -----Original Message-----
> > From: Lab Candidate [mailto:labccie@yahoo.com]
> > Sent: Thursday, February 14, 2002 1:48 PM
> > To: Xu, James; ccielab@groupstudy.com
> > Subject: Re: How route redistribution EXACTLY works --- need
> > confirmation
> >
> >
> > James,
> >
> > I don't think there's such a thing as RIP route database.
> > The RIP process will pick up routes directly from the
> > routing table, whereas ospf picks from its database.
> >
> > ---
> >
> > --- "Xu, James" <james.xu@eds.com> wrote:
> > > All:
> > >
> > > It has been and still puzzling me how a routing process pick routes
and
> > > redistribute them into another routing process and vice versa? As an
> > > example, mutual redistribution between RIP and OSPF in a router:
> > >
> > > Here is my experience and explanation:
> > >
> > > 1). The RIP process picks all RIP routes inside its database, and
> > > redistributes these routes into OSPF routing process.
> > > 2). OSPF process picks all OSPF routes in the OSPF database, and
> > > redistributes these routes into RIP routing process.
> > >
> > > During the redistribution, the split-horizon rule appies, meaning the
> > newly
> > > redistributed routes from RIP into OSPF will not be redistributed back
> > into
> > > RIP right away, and vice versa.
> > >
> > > Any input are appreciated, especially some links for this mechnism.
> > >
> > > James
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