Re: OSPF Order of Preference

Federico,

When there are 2 NSSA ABRs redistributing the same external network to Area
0, then router has to choose either E1/E2 -vs- N1/N2.

In such cases, router goes thru the steps Nick listed.

-Naveen.

On Tue, Jul 7, 2009 at 5:52 AM, Federico Cossu <federico.cossu_at_gmail.com>wrote:

> hi all,
> i wondering about which type of router a type-5 LSA and a type-7 LSA
> can be found for the same destination.
> does this could happen only on an ASBR/NSSAtranslator only?
> thanks
>
> 2009/7/4 Lejoe <styran_at_gmail.com>:
> > Hi,
> >
> > Yes ofcourse E1 will always be preferred over N1 (if both N1 and E1 have
> > same cost) . I was talking about two E1s with Fowarding address set and
> > without forwarding address set (FW:0.0.0.0)
> >
> >
> > Lejoe
> >
> > On Sat, Jul 4, 2009 at 6:51 PM, Nicholas Davitashvili
> > <nickda_at_gmail.com>wrote:
> >
> >> I recently saw a scenario, where two routes(E1 and N1) having Equal
> Cost,
> >> were load balancing.
> >> As soon as N1 was stripped of its FA, E1 became a preferred route.
> >>
> >> Nick
> >> GREENNET
> >> Lat: 41043'25.46"N
> >> Long: 44045'45.60"E
> >>
> >>
> >>
> >> On Sat, Jul 4, 2009 at 11:51 AM, Lejoe <styran_at_gmail.com> wrote:
> >>
> >>> Hi Nick,
> >>>
> >>> I dont think the Forwarding Address should be part of the criteria
> because
> >>> when two type 5 LSAs (assuming E1) to the same destination exists, one
> > with
> >>> FW address set and the other without.
> >>>
> >>> In this case, the LSA to be installed in the routing table of a router
> is
> >>> based on the comparison that router's metric to the ASBR that generated
> > the
> >>> LSA with a forwarding address of 0.0.0.0 to that router's metric to
> reach
> >>> the forwarding address of X , which was set for the LSA generated by
> the
> >>> ASBR.
> >>>
> >>> Now assuming the metric was equal, I would believe the result is load
> >>> balancing across the two paths. Hope that someone can shed more light
> on
> >>> this. (equal costs with FW and without FW)
> >>>
> >>>
> >>> Regards
> >>>
> >>> Lejoe
> >>>
> >>>
> >>> On Sat, Jul 4, 2009 at 5:00 PM, Nicholas Davitashvili
> > <nickda_at_gmail.com>wrote:
> >>>
> >>>> Additional criteria of course would be that costs are equal.
> >>>>
> >>>> Nick
> >>>> GREENNET
> >>>> Lat: 41043'25.46"N
> >>>> Long: 44045'45.60"E
> >>>>
> >>>>
> >>>> On Sat, Jul 4, 2009 at 10:26 AM, Nicholas Davitashvili
> >>>> <nickda_at_gmail.com>wrote:
> >>>>
> >>>> > Hi Group,
> >>>> >
> >>>> > If anyone can confirm this order of preference in OSPF, I'd be
> really
> >>>> > greatful.
> >>>> > If it is wrong, please give the correct order:
> >>>> >
> >>>> > 1. O - OSPF Intra-Area
> >>>> > 2. IA - OSPF Inter-Area
> >>>> > 3. E1 /w FA -- External Type 1 With Forwarding Address
> >>>> > 4. N1 /w FA
> >>>> > 5. E1 /wo FA -- Ext. Type 1 with Forwarding Address set to 0.0.0.0
> >>>> > 6. N1 /wo FA
> >>>> > 7. E2 /w FA
> >>>> > 8. N2 /w FA
> >>>> > 9. E2 /wo FA
> >>>> > 10. N2 /wo FA
> >>>> >
> >>>> > Thanks in advance!
> >>>> >
> >>>> > Nick
> >>>> > GREENNET
> >>>> > Lat: 41043'25.46"N
> >>>> > Long: 44045'45.60"E
> >
> >
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Received on Tue Jul 07 2009 - 10:54:46 ART