[j-nsp] track-igp-metric in LDP

[Chen Jiang]

Hi! Dave

Thanks for clarifying. So you mean BGP path selection tie breaker for IGP
metric is happening in inet.3(LDP) but not inet.0(IGP like OSPF/IOSIS), so
we need "track-igp-metric" to introduce metric into LDP for
track-igp-metric. is it correct?

BR!

James Chen

On Sun, Aug 2, 2020 at 8:17 PM Dave Bell <me at geordish.org> wrote:

> If you are running next hop self on your BGP routes at the edge, the best
> path will be via a loopback in an  LSP.
>
> If you have two identical routes, one of the tie breakers is IGP
> preference. If that knob isn’t set the IGP cost will be 1 for everything,
> and you will progress down to less helpful tue breakers like router id.
>
> Regards,
> Dave
>
> On Sun, 2 Aug 2020 at 11:58, Chen Jiang <ilovebgp4 at gmail.com> wrote:
>
>> Hi! Michael
>>
>> Thanks for your clarification.
>>
>> Sure, it will let LDP use IGP metric, but is there any benefit?
>>
>> Cause per my understanding LDP only works for label distributing, not path
>> selection, and LDP always follows the IGP path, so what is the difference
>> or benefit to add additional configuration knob to let LDP use IGP metric?
>>
>> BR!
>>
>> Chen Jiang
>>
>> On Sun, Aug 2, 2020 at 6:32 PM Michael Hallgren <mh at xalto.net> wrote:
>>
>> > Hi James,
>> >
>> > From memory, Junos assigns metric 1 by default to "LDP routes", not IGP
>> > metric, unless you push this button.
>> >
>> > Cheers,
>> > mh
>> > ------------------------------
>> > *De :* Chen Jiang <ilovebgp4 at gmail.com>
>> > *Envoyé :* dimanche 2 août 2020 12:10
>> > *À :* Juniper List
>> > *Objet :* [j-nsp] track-igp-metric in LDP
>> >
>> > Hi! Experts
>> >
>> > Sorry for disturbing, I am curious about track-igp-metric knob under
>> LDP,
>> > is there any scenarios it will be useful? I think ldp is just a label
>> > distribution protocol, the forwarding path always follows the IGP
>> shortest
>> > path, is there any benefit for using track-igp-metric?
>> >
>> > Thanks for your help!
>> >
>> > --
>> > BR!
>> >
>> >
>> >
>> >            James Chen
>> > _______________________________________________
>> > juniper-nsp mailing list juniper-nsp at puck.nether.net
>> > https://puck.nether.net/mailman/listinfo/juniper-nsp
>> >
>>
>>
>> --
>> BR!
>>
>>
>>
>>            James Chen
>> _______________________________________________
>> juniper-nsp mailing list juniper-nsp at puck.nether.net
>> https://puck.nether.net/mailman/listinfo/juniper-nsp
>>
>

-- 
BR!



           James Chen