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

Rob Foehl rwf at loonybin.net
Wed Sep 26 18:20:00 EDT 2018

On Mon, 10 Sep 2018, Ivan Malyarchuk wrote:

> 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.

Just hit this issue with 17.4R2 on a newly installed RE-S-X6-64G.  PIC 
works fine as long as all routes are equivalent local preference; as soon 
as one arrives with a lower preference, the #Multipath entry appears with 
all higher preference routes installed as equivalent active routes and the 
lower preference as the sole inactive:

         #Multipath Preference: 255
                 Protocol next hop: [X]
                 Indirect next hop: 0x940dc00 1048575 INH Session ID: 0x143 Weight 0x1
                 Protocol next hop: [Y]
                 Indirect next hop: 0x940da00 1048574 INH Session ID: 0x142 Weight 0x1
                 Protocol next hop: [Z]
                 Indirect next hop: 0x9411800 1048624 INH Session ID: 0x161 Weight 0x4000
                 State: <ForwardingOnly Int Ext>
                 Inactive reason: Forwarding use only

In this case, [X] has a greater IGP cost than [Y], and the BGP decision 
is correct, but [X] is still installed in the forwarding table as an 
active route.

Anyone have any PRs or existing tickets they'd be willing to share 
(off-list is fine) for purposes of sending JTAC in the right direction?


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