[FROG] Routes learned from iBGP are not maintaining Metrics when advertised to eBGP peers

[Lee Clements]

Doing some testing on FRR here, and hoping for some assistance.  Hopefully
this is the right place to go.  If not, please let me know!

I've got 3 remote iBGP peers that are configured as standard iBGP peers.
These two iBGP peers learn some routes locally and then re-advertise these
prefixes over a full-mesh iBGP network to each other, with FRR being one of
the four routers in the mesh.  The other three iBGP peers are Cisco.

FRR has one eBGP peer, to replicate re-advertising these routes out to
iBGP.  In our other three iBGP peers, we leverage route-maps to increment
the received MED value of the route, so that we can prefer locally received
eBGP routes - all else being equal - as opposed to those learned from our
iBGP speakers in other locations.  We also do this so locally originated
prefixes from our AS have a higher metric when going out to eBGP speakers
so they don't inadvertently get preferenced when there's a better path for
the route to take.

I am receiving the routes from our iBGP speakers fine, and see the
incremented MED on receipt of the routes from the aforementioned speaker.
When I configure a local (to FRR) iBGP speaker as a route-reflector-client
within the same AS, these pre-incremented MED's are correctly advertised to
the local iBGP speaker and work just fine.

When advertising these same prefixes to an eBGP speaker with a different
AS, the metric's are not readvertised, and only a locally originated prefix
maintains any sort of metric at all.

Route's received from one of our remote iBGP speakers:

routert# sh bgp ipv4 unicast neighbors 1.1.1.1 received-routes
BGP table version is 0, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 1234
Status codes:  s suppressed, d damped, h history, * valid, > best, =
multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 0.0.0.0/0         1.1.1.1                           100    100      0 i
*> 1.2.3.0/20       1.1.1.1                           100    100      0 i
*> 2.3.4.0/21       1.1.1.1                           100    100      0
5678 i
*> 3.4.5.0/24       1.1.1.1                           100    100      0
5678 i
*> 5.6.7.0/22       1.1.1.1                           102    100      0
5678 i
*> 7.8.9.0/24       1.1.1.1                           102    100      0
5678 i

Total number of prefixes 6

Route's being correctly re-advertised and maintaining metric on
re-advertisement to our local iBGP speaker (route-reflector-client):

router# sh bgp ipv4 unicast neighbors 3.3.3.3 advertised-routes
BGP table version is 4560509, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 1234
Status codes:  s suppressed, d damped, h history, * valid, > best, =
multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 1.2.3.0/20   1.1.1.1              100    100      0 i
*> 1.2.7.0/23   2.2.2.2              0    100  32768 i
*> 2.3.4.0/21   1.1.1.1              100    100      0 5678i
*> 3.4.5.0/24   1.1.1.1              100    100      0 5678 i
*> 5.6.7.0/22   1.1.1.1              102    100      0 5678 i
*> 7.8.9.0/24   1.1.1.1              102    100      0 5678 i

Total number of prefixes 6

Route's not maintaining their metric on re-advertisement to our local (to
FRR) eBGP speaker:

router# sh bgp ipv4 unicast neighbors 8.8.8.8 advertised-routes
BGP table version is 4562244, local router ID is 2.2.2.2, vrf id 0
Default local pref 100, local AS 1234
Status codes:  s suppressed, d damped, h history, * valid, > best, =
multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 1.2.3.0/20  0.0.0.0                                   100      0 i
*> 1.2.7.0/23  0.0.0.0                        0                  32768 i
*> 2.3.4.0/21  0.0.0.0                                    100      0 5678i
*> 3.4.5.0/24  0.0.0.0                                    100      0 5678 i
*> 5.6.7.0/22  0.0.0.0                                    100      0 5678 i
*> 7.8.9.0/24  0.0.0.0                                    100      0 5678 i

Total number of prefixes 6

Am I doing something wrong here?  Otherwise a pretty straight forward BGP
setup with some basic route-maps in and out, nothing too crazy.  Is this
expected behavior in FRR?

Running latest available stable release, FRRouting 7.1RPKI.

Thanks for any help.
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