[j-nsp] "set routing-options protect core" breaks local-preference

[Ivan Malyarchuk]

Hi. We also find something wrong with "protect core".
Seems like Junos 18.1 and 18.2 (running on MX204 in our case) makes one #Multipath  equal-cost group with ALL paths except one worst AND one with worst path - as backup.

I think it must create  #Multipath forwarding-only route with one best (active, with weight of nexthop 0x1, find in detail output) and one "second best" path as backup (with weight 0x4000). However I cant find any public PR or Known Issues references in 18.x release notes nor in prsearch.


10 сентября 2018 г., 19:10, "Karl Gerhard" <karl_gerh at gmx.at> написал:

> Hello
> 
> I am experimenting with BGP PIC before deploying it to production and I have found an oddity:
> With "set routing-options protect core" local-preference stops working the way I would expect it to
> work.
> 
> If I configure "local-preference 120" on import from my IBGP neighbor the router will send traffic
> for some prefixes to my IBGP neighbor (where they will egress through EBGP) and for other prefixes
> directly to my EBGP neighbor. It seems like they're getting load-balanced per destination subnet.
> This is how it looks in the routing table:
> 
> root at router1# run show route 1.0.143.0/24 table inet.0
> inet.0: 705394 destinations, 2116034 routes (705393 active, 0 holddown, 2 hidden)
> @ = Routing Use Only, # = Forwarding Use Only
> + = Active Route, - = Last Active, * = Both
> 
> 1.0.143.0/24       @[BGP/170] 00:08:21, localpref 120
> AS path: 174 38040 23969 ?, validation-state: unverified
>> to 123.123.123.1 via ae1.0
> to 55.55.55.2 via ae3.0
> [BGP/170] 00:07:37, localpref 100
> AS path: 174 38040 23969 ?, validation-state: unverified
>> to 55.55.55.2 via ae3.0
> #[Multipath/255] 00:07:37, metric2 0
> to 123.123.123.1 via ae1.0
>> to 55.55.55.2 via ae3.0
> to 55.55.55.2 via ae3.0
> 
> 123.123.123.1 is my IBGP neighbor where I would like traffic to go
> 55.55.55.2 is my EBGP neighbor
> 
> This is the part that is causing issues:
> #[Multipath/255] 00:07:37, metric2 0
> to 123.123.123.1 via ae1.0
>> to 55.55.55.2 via ae3.0
> to 55.55.55.2 via ae3.0
> 
> With "local-preference 120" configured on my IBGP session I would expect all packets to go to my
> IBGP neighbor (123.123.123.1) - at least that's how it used to work. But for this specific subnet
> (and many others) the traffic will go directly to my EBGP neighbor.
> 
> How do I make all traffic go to my IBGP neighbor?
> Is that "by design" or is it a bug in Junos 18.2R1?
> 
> Regards
> Karl
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp




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С уважением,
Иван Малярчук
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