[c-nsp] OSPF per-prefix LFA

[Dan Peachey]

On 28 May 2015 at 13:17, Mohammad Khalil <eng_mssk at hotmail.com> wrote:

> 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
>
>
The backup path is already installed in the RIB/FIB - the active path
should be removed as soon as the link down is detected which should be
pretty much instant. I'd expect you to see the route change straight away
but maybe something funky is happening because it's a virtualised
environment? I'm not sure as I've only used it in hardware environments.

I've tested end to end convergence across a network with LFA before and it
came in at under 100ms.

If you don't have it already, you can try 'carrier-delay msec 0' on the
ethernet interfaces. Not sure it will make a difference but worth a stab in
the dark.

Dan