[c-nsp] OSPF per-prefix LFA

[Dan Peachey]

On 28 May 2015 at 12:24, Mohammad Khalil <eng_mssk at hotmail.com> wrote:

> Hi all
> I am trying to test the feature
> My topology consists of three routers (one of them is CSR1000v) and the
> other two are 3725 all simulated via GNS3
>
> R1(CSR) is connected to R2 and R3 , there is a direct connection as well
> between R2 and R3
> All routers are configured with a loopback interface with the form of
> x.x.x.x/32 where x is the router number
>
> Now , R1 is learning R2 loopback interface normally and logically through
> the direct link with R2
>
> When I shutdown the interface with R2 (as I do not want to turn off the
> remote interface on R2 as I cannot turn on BFD on GNS3) and I have checked
> the route to 2.2.2.2 , it took about 5-6 seconds to install the same route
> via the backup path (via R3)
>
> Now , I have configured the feature on the CSR
> CSR(config)#router ospf 1
> CSR(config-router)#fast-reroute per-prefix enable area 0 prefix-priority
> high
>
> And I repeat the same test it took about 4 seconds to learn the prefix via
> the backup path
>
> Is this the expected behavior or it should be less than that?
>
> Thanks in advance
>
> BR,
> Mohammad
>
>

Hi Mohammed,

What's the output of 'show ip repair-paths' and 'show ip cef 2.2.2.2' on R1
when the link between R1 and R2 is up? You should see an RPR route for R2
loopback via R3.

If you don't see any RPR route, you may also need to force prefix-priority
of loopbacks to high with something like:

ip prefix-list LOOPBACK-PREFIXES seq 5 permit 2.2.2.2/32
!
route-map OSPF-SPF-PRIORITY permit 10
 match ip address prefix-list LOOPBACK-PREFIXES
!
router ospf 1
 prefix-priority high route-map OSPF-SPF-PRIORITY
!

I've had to do this on IOS before - not sure about XE.

Thanks,

Dan