[j-nsp] ISIS-OSPF Redistribution Questions

[Hoogen]

What is your topology?.. Is your topology is similar to the book?? The
questions do seem a bit awkward... Well yeah NSSA def route is like an
external route so changing the value affects everything... and for ISIS
level 1 preference can be set specifically and def route generated by ISIS
(Book Case Study) is level 1.

Thinking about it... The only way you can do things is using preference
values.. since OSPF nor ISIS can have an import policy. So in this scenario
of yours you might not have optimal routing.. It is a loop..if you do have
to put that level 1 external preference as 149...

Another way to just solve your problem would be to have static routes... to
the ABR's.

-Hoogen

On Sun, Nov 8, 2009 at 12:38 AM, Walaa Abdel razzak <walaaez at bmc.com.sa>wrote:

>  Hi
>
> If I did this, then R6 or R7 will prefer datacenter routes through R5 bcoz
> they r coming with lower preference than ISIS routes which make sub-optimal
> routing.
>
>
> Best Regards,
> Walaa Abdel Razzak
>
>
> -----Original Message-----
> From: Hoogen [mailto:hoogen82 at gmail.com <hoogen82 at gmail.com>]
> Sent: Sat 07/11/2009 22:38
> To: Walaa Abdel razzak
> Cc: juniper-nsp at puck.nether.net
> Subject: Re: [j-nsp] ISIS-OSPF Redistribution Questions
>
> Hi,
>
> Your scenario looks like a complete opposite of what we have in the case
> study, from what you have mentioned here.. The solution would be that on R6
> and R7 you set the ospf external-preference to be lower than 149.. This
> would make the def route from OSPF more preferred.
>
> set protocols ospf external-preference 148 <-- Make the nssa def route
> preference on R6 and R7 to be lower than that received from the ISIS DC
> router.
>
> -Hoogen
>
> 2009/11/7 Walaa Abdel razzak <walaaez at bmc.com.sa>
>
> > Hi Experts
> >
> >
> >
> > If you have area 2 nssa receiving default route from the ABR with metric
> > 150, two routers R6, R7 are sending this default route to ISIS level 1
> > router in the DC. The L1 external preference are modified on R6, R7 to be
> > 149. This is to prefer routes coming from ISIS than OSPF. The problem is
> > that DC router resend the default route from R6 to R7. R7 see it with
> > preference of 149 and the default route is coming from OSPF is 150 so it
> > prefers the ISIS which cause non-optimal routing. Any ideas to solve this
> > issue without making modification on the DC router?
> >
> >
> >
> > Sample config:
> >
> >
> >
> > R6 or R7 config.:
> >
> > --------------------
> >
> > isis {
> >
> >    export senddefault;           --------à send default to the ISIS
> router
> >
> >    level 2 disable;
> >
> >    level 1 external-preference 149;
> >
> >    interface fe-1/3/1.23;
> >
> >    interface lo0.6;
> >
> > }
> >
> > ospf {
> >
> >    export fromisis;                 --------à redistribute routes from
> ISIS
> >
> >    area 0.0.0.2 {
> >
> >        nssa;
> >
> >        interface lo0.6;
> >
> >        interface fe-1/3/0.20;
> >
> >        interface fe-1/3/1.16;
> >
> >        interface fe-1/3/1.23 {
> >
> >            passive;
> >
> >        }
> >
> >    }
> >
> > }
> >
> >
> >
> > DC:
> >
> > -----
> >
> > isis {
> >
> >    export static-isis;
> >
> >    level 2 disable;
> >
> >    interface fe-1/3/0.23;
> >
> >    interface fe-1/3/0.24;
> >
> > }
> >
> >
> >
> > BR,
> >
> > Walaa Abdel Razzak
> >
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>
>