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To: freebsd-net@freebsd.org
From: Tobias Urdin <tobias.urdin@binero.se>
Subject: ospf redistribute into openbgpd overwrites directly connected routes
Message-ID: <9507d752-6815-92fe-924b-55459710bb9d@binero.se>
Date: Mon, 30 Jul 2018 16:06:02 +0200
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Hello,

I have a setup where we connect a OSPF area with a edge router, this 
edge router then has a BGP peer to my router
where it redistributes all OSPF routes into the BGP feed to my router.

My router is running FreeBSD 11.1 with openbgpd

root@myrouter:~ # uname -a
FreeBSD dr20-1-sto1 11.1-RELEASE FreeBSD 11.1-RELEASE #0 r321309: Fri 
Jul 21 02:08:28 UTC 2017 
root@releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64

root@myrouter:~ # pkg info openbgpd
openbgpd-5.2.20121209_2
Name           : openbgpd
Version        : 5.2.20121209_2

The thing here is that my router has layer 2 access directly to one of 
the networks that the edge router BGP announces to my router 
(172.20.104.0/22).
When my FreeBSD machine boots it will install a directly connected route 
for 172.20.104.0/22 in my routing table but as soon as openbgpd starts 
it will
install a 172.20.104.0/22 route with the nexthop of the edge router instead.

How can I prevent openbgpd from overwriting the directly connected route?
Directly connected networks should never be overwritten by a routing 
protocol but I suspect this is because of the redistribute.

I've tried messing with metrics, but maybe I to create a rtable and mess 
around with that?
Output of some info is below.

Best regards
Tobias

root@myrouter:~ # bgpctl show fib connected | grep 104
*C      48 172.20.104.0/22      link#10

root@myrouter:~ # route get 172.20.104.100
    route to: 172.20.104.100
destination: 172.20.104.0
        mask: 255.255.252.0
     gateway: edgerouter
         fib: 0
   interface: vlan10
       flags: <UP,GATEWAY,DONE,PROTO1,PINNED>
  recvpipe  sendpipe  ssthresh  rtt,msec    mtu        weight expire
        0         0         0         0      1500         1         0

root@myrouter:~ # ifconfig vlan10
vlan10: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> 
metric 0 mtu 1500
options=600703<RXCSUM,TXCSUM,TSO4,TSO6,LRO,RXCSUM_IPV6,TXCSUM_IPV6>
         ether x
         inet 172.20.107.253 netmask 0xfffffc00 broadcast 172.20.107.255
         inet 172.20.107.254 netmask 0xfffffc00 broadcast 172.20.107.255 
vhid 2
         nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
         media: Ethernet autoselect (10Gbase-Twinax 
<full-duplex,rxpause,txpause>)
         status: active
         vlan: 10 vlanpcp: 0 parent interface: ix1
         carp: MASTER vhid 2 advbase 1 advskew 10
         groups: vlan

root@myrouter:~ # cat /etc/rc.conf
...snip..
ifconfig_vlan10="inet 172.20.107.253 netmask 255.255.252.0 vlan 10 
vlandev ix1"
ifconfig_vlan10_alias0="inet vhid 2 advskew 100 pass test123 alias 
172.20.107.254/22"

root@myrouter:~ # cat /usr/local/etc/bgpd.conf
...snip...
group "peering ASxxxx" {
   remote-as xxxx
   softreconfig in yes

   neighbor edgerouter {
     announce self
     descr "AS xxxx edgerouter"
     local-address xxxx
     depend on <outside int>
   }
}
...snip...