[j-nsp] BGP import policy quirk within VRF

[Jeff S Wheeler]

I believe my BGP import policy is being evaluated twice on routes learnt
from VRF BGP neighbors, upon installation into other routing-instances.

I use as-path-groups to raise/lower local-preference upon import from
BGP neighbors.  Below is a route that should have its local-preference
adjusted to 95 through a "subtract 5."  That is what happens in the
verio transit VRF, however in the inet.0 table, which learns the route
by belonging to the rib-group referenced in the VRF BGP configuration,
the "subtract 5" action seems to be happening twice, resulting in a
local-preference of 100 - 5 - 5 == 90, not 100 - 5 == 95.

This would affect users who provide transit and L3VPN and learn one or
more Internet routes from their customer on the PE-CE BGP session.
Maybe no one is doing this because it would be too complex for customers
to get their heads around, but I believe it is a buggy behavior.

I have also duplicated the problem on JUNOS 8.5R1.14 with basically
identical configuration.

Is this a known issue?

7.6R1.9> show route www.sprintlink.net terse 

inet.0: 266652 destinations, 670468 routes (266652 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

A Destination        P Prf   Metric 1   Metric 2  Next hop        AS path
* 208.0.0.0/11       B 170        100          1 >A.B.C.S        1239 I
                     B 170         90          1 >A.B.C.V        2914 1239 I

verio.inet.0: 261751 destinations, 261753 routes (261751 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

A Destination        P Prf   Metric 1   Metric 2  Next hop        AS path
* 208.0.0.0/11       B 170         95          1 >A.B.C.V         2914 1239 I

sprint.inet.0: 262240 destinations, 262241 routes (262240 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

A Destination        P Prf   Metric 1   Metric 2  Next hop        AS path
* 208.0.0.0/11       B 170        100          1 >A.B.C.S         1239 I

[edit policy-options]
7.6R1.9# show as-path-group verio-prefdn5     
as-path _placeholder "^$";
as-path sprint ".* 1239 .*";
as-path att ".* 1239 .*";
as-path lvlt ".* 3356 .*";

-- 
Jeff S Wheeler <jsw at inconcepts.biz> +1-212-981-0607
Sr Network Operator  /  Innovative Network Concepts