Hello, thank you for your help. 

The next day after the failure, I restart ospf_business on faulty r2. Discovery can be seen from r0 sent over the default route on r2 routing table. I was very surprised, and why? Next, how do I troubleshoot? 

r0 is a Layer 3 switch. 

The following is the recovery seen in r0-2 status. 

r1: 

bird> show ospf state all ospf_business 

1016 - 

     area 0.0.0.20 

      

     router x.y.z.1 

     distance 10 

     network x.y.z.0/28 metric 1 

     external 0.0.0.0 / 0 metric2 1 tag 00000001 

      

     router x.y.z.3 

     distance 0 

     network x.y.z.0/28 metric 10 

     external a.b.c.d/25 metric2 20 via x.y.z.1 

      

     network x.y.z.0/28 

     dr x.y.z.3 

     distance 10 

     router x.y.z.3 

     router x.y.z.1 

r2: 

bird> show ospf state all ospf_business 

1016 - 

     area 0.0.0.30 

      

     router x.y.z.17 

     distance 10 

     network x.y.z.16/28 metric 1 

     external 0.0.0.0 / 0 metric2 1 tag 00000001 

      

     router x.y.z.19 

     distance 0 

     network x.y.z.16/28 metric 10 

      

     network x.y.z.16/28 

     dr x.y.z.17 

     distance 10 

     router x.y.z.17 

     router x.y.z.19 

r0: 

<r0-switch> display ospf brief 

OSPF Process 100 with Router ID x.y.z.1 

OSPF Protocol Information 

 RouterID: x.y.z.1 Border Router: AS 

 Multi-VPN-Instance is not enabled 

 Graceful-restart capability: disabled 

 Helper support capability: not configured 

 Spf-schedule-interval: max 10000ms, start 500ms, hold 1000ms 

 Default ASE parameters: Metric: 1 Tag: 1 Type: 2 

 Route Preference: 10 

 ASE Route Preference: 150 

 SPF Computation Count: 62 

 RFC 1583 Compatible 

 Retransmission limitation is disabled 

 Area Count: 1 Nssa Area Count: 0 

 ExChange / Loading Neighbors: 0 

 Process total up interface count: 1 

 Process valid up interface count: 1 

  

 Area: 0.0.0.20 

 Authtype: None Area flag: Normal 

 SPF scheduled Count: 62 

 ExChange / Loading Neighbors: 0 

 Router ID conflict state: Normal 

 Area interface up count: 1 

 Interface: x.y.z.1 (Vlanif3) 

 Cost: 1 State: BDR Type: Broadcast MTU: 1500 

 Priority: 1 

 Designated Router: x.y.z.3 

 Backup Designated Router: x.y.z.1 

 Timers: Hello 10, Dead 40, Poll 120, Retransmit 5, Transmit Delay 1 

OSPF Process 200 with Router ID x.y.z.17 

OSPF Protocol Information 

 RouterID: x.y.z.17 Border Router: AS 

 Multi-VPN-Instance is not enabled 

 Graceful-restart capability: disabled 

 Helper support capability: not configured 

 Spf-schedule-interval: max 10000ms, start 500ms, hold 1000ms 

 Default ASE parameters: Metric: 1 Tag: 1 Type: 2 

 Route Preference: 10 

 ASE Route Preference: 150 

 SPF Computation Count: 53 

 RFC 1583 Compatible 

 Retransmission limitation is disabled 

 Area Count: 1 Nssa Area Count: 0 

 ExChange / Loading Neighbors: 0 

 Process total up interface count: 1 

 Process valid up interface count: 1 

  

 Area: 0.0.0.30 

 Authtype: None Area flag: Normal 

 SPF scheduled Count: 53 

 ExChange / Loading Neighbors: 0 

 Router ID conflict state: Normal 

 Area interface up count: 1 

 Interface: x.y.z.17 (Vlanif4) 

 Cost: 1 State: DR Type: Broadcast MTU: 1500 

 Priority: 1 

 Designated Router: x.y.z.17 

 Backup Designated Router: x.y.z.19 

 Timers: Hello 10, Dead 40, Poll 120, Retransmit 5, Transmit Delay 1 

The following is r0 configurations: 

interface Vlanif3 

 ip address x.y.z.1 255.255.255.240 

 ospf authentication-mode md5 1 cipher pass1 

# 

interface Vlanif4 

 ip address x.y.z.17 255.255.255.240 

 ospf authentication-mode md5 1 cipher pass2 

# 

ospf 100 router-id x.y.z.1 

 description business about bussiness1 

 default-route-advertise 

 area 0.0.0.20 

  network x.y.z.0 0.0.0.15 

# 

ospf 200 router-id x.y.z.17 

 description business about bussiness2 

 default-route-advertise 

 area 0.0.0.30 

    network x.y.z.16 0.0.0.15 

# 

ip route-static 0.0.0.0 0.0.0.0 q.w.e.r