[c-nsp] OSPF per-prefix LFA

[Mohammad Khalil]

Hi

Now , the main link is active again with hello/dead intervals adjsuted

CSR#sh ip ospf interface gigabitEthernet 1 | inc Dead
  Timer intervals configured, Hello 1, Dead 4, Wait 4, Retransmit 5

R2#sh ip ospf int f0/0 | inc Dead
  Timer intervals configured, Hello 1, Dead 4, Wait 4, Retransmit 5

CSR#sh ip route 2.2.2.2
Routing entry for 2.2.2.2/32
  Known via "ospf 1", distance 110, metric 2, type intra area
  Last update from 192.168.12.2 on GigabitEthernet1, 00:01:33 ago
  Routing Descriptor Blocks:
  * 192.168.12.2, from 2.2.2.2, 00:01:33 ago, via GigabitEthernet1
      Route metric is 2, traffic share count is 1
      Repair Path: 192.168.13.3, via GigabitEthernet2

CSR#sh ip cef 2.2.2.2
2.2.2.2/32
  nexthop 192.168.12.2 GigabitEthernet1
    repair: attached-nexthop 192.168.13.3 GigabitEthernet2

CSR#sh ip route repair-paths 2.2.2.2
Routing entry for 2.2.2.2/32
  Known via "ospf 1", distance 110, metric 2, type intra area
  Last update from 192.168.12.2 on GigabitEthernet1, 00:02:08 ago
  Routing Descriptor Blocks:
  * 192.168.12.2, from 2.2.2.2, 00:02:08 ago, via GigabitEthernet1
      Route metric is 2, traffic share count is 1
      Repair Path: 192.168.13.3, via GigabitEthernet2
    [RPR]192.168.13.3, from 2.2.2.2, 00:02:08 ago, via GigabitEthernet2
      Route metric is 3, traffic share count is 1

The outputs as I understood the feature is fine and backup route is in place , but I was asking about the time it should take the backup path to be installed in the RIB?

Thanks again

BR,
Mohammad

> Date: Thu, 28 May 2015 13:02:08 +0100
> From: dan at illusionnetworks.com
> To: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] OSPF per-prefix LFA
> 
> 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
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