WALKTHROUGH: Router LSAs

So you're stuck or don't trust your work. Here is the cheat/check page. Note that this is all done from the perspective of J2300-1. Adapt to other routers as needed.

  1. For each area your router is connected to, count how many Type 1 LSAs exist in the LSDB
    2. admin@J2300-1> show ospf database area 0 router    

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x80000049  1722  0x22 0x938d  72
Router   10.0.0.2         10.0.0.2         0x8000002b   140  0x22 0xac76  72
Router   10.0.0.3         10.0.0.3         0x80000029  1829  0x22 0x8c08  84
Router   10.0.0.4         10.0.0.4         0x80000019  2255  0x22 0x9ed3  84
Router   10.0.0.5         10.0.0.5         0x80000018  1680  0x22 0x3380  72
Router   10.0.0.6         10.0.0.6         0x80000016  1042  0x22 0x504c  72

admin@J2300-1> show ospf database area 0 router | match ^Router | count 
Count: 6 lines

admin@J2300-1> admin@J2300-1> show ospf database area 1 router                            

    OSPF database, Area 0.0.0.1
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x8000001a  1454  0x22 0x8d4d  36
Router   10.0.0.3         10.0.0.3         0x80000007  1120  0x22 0x88a   36
Router   10.1.0.1         10.1.0.1         0x80000022   338  0x22 0xcb8a  60
Router   10.1.0.2         10.1.0.2         0x8000001b   341  0x22 0xf43c  60
Router   10.1.0.3         10.1.0.3         0x80000018   340  0x22 0x7da4  72
Router   10.1.0.4         10.1.0.4         0x8000001a   339  0x22 0x4ae5  72

admin@J2300-1> show ospf database area 1 router | match ^Router | count 
Count: 6 lines

admin@J2300-1>
  2. Examine the Router LSA that your router is originating for the backbone area
    3. admin@J2300-1> show ospf database area 0 router                            

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x80000049  1844  0x22 0x938d  72
Router   10.0.0.2         10.0.0.2         0x8000002b   262  0x22 0xac76  72
Router   10.0.0.3         10.0.0.3         0x80000029  1951  0x22 0x8c08  84
Router   10.0.0.4         10.0.0.4         0x80000019  2377  0x22 0x9ed3  84
Router   10.0.0.5         10.0.0.5         0x80000018  1802  0x22 0x3380  72
Router   10.0.0.6         10.0.0.6         0x80000016  1164  0x22 0x504c  72

admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.1 detail 

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x80000049  1852  0x22 0x938d  72
  bits 0x1, link count 4
  id 10.0.12.2, data 10.0.12.1, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.0.3, data 10.0.13.1, Type PointToPoint (1)
    Topology count: 0, Default metric: 5
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 5
  id 10.0.0.1, data 255.255.255.255, Type Stub (3)
    Topology count: 0, Default metric: 0
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.0.0.3
      Metric: 5, Bidirectional
    Type: Transit, Node ID: 10.0.12.2
      Metric: 5, Bidirectional

admin@J2300-1> 
[edit]
  3. Compare the number of PointToPoint (Type 1) links and and Transit (Type 2) links to your configuration
    4. admin@J2300-1> show ospf interface area 0 | match PtToPt 
fxp1.13             PtToPt  0.0.0.0         0.0.0.0         0.0.0.0            1

admin@J2300-1> show ospf interface area 0 | match DR        
Interface           State   Area            DR ID           BDR ID          Nbrs
fxp1.12             BDR     0.0.0.0         10.0.0.2        10.0.0.1           1
lo0.0               DR      0.0.0.0         10.0.0.1        0.0.0.0            0

admin@J2300-1>
  4. Compare the number and contents of the of Stub (Type 3) links to the addressing on your links
    5. admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.1 detail    

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x8000004a   329  0x22 0x918e  72
  bits 0x1, link count 4
  id 10.0.12.2, data 10.0.12.1, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.0.3, data 10.0.13.1, Type PointToPoint (1)
    Topology count: 0, Default metric: 5
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 5
  id 10.0.0.1, data 255.255.255.255, Type Stub (3)
    Topology count: 0, Default metric: 0
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.0.0.3
      Metric: 5, Bidirectional
    Type: Transit, Node ID: 10.0.12.2
      Metric: 5, Bidirectional

admin@J2300-1> show interfaces terse fxp1.12 
Interface               Admin Link Proto    Local                 Remote
fxp1.12                 up    up   inet     10.0.12.1/24    

admin@J2300-1> show interfaces terse lo0.0      
Interface               Admin Link Proto    Local                 Remote
lo0.0                   up    up   inet     10.0.0.1            --> 0/0

admin@J2300-1>
  5. Inspect the point-to-point link in your Router LSA and node the LSA ID and the LSA data
    6. admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.1 detail    

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x8000004a  1187  0x22 0x918e  72
  bits 0x1, link count 4
  id 10.0.12.2, data 10.0.12.1, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.0.3, data 10.0.13.1, Type PointToPoint (1)
    Topology count: 0, Default metric: 5
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 5
  id 10.0.0.1, data 255.255.255.255, Type Stub (3)
    Topology count: 0, Default metric: 0
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.0.0.3
      Metric: 5, Bidirectional
    Type: Transit, Node ID: 10.0.12.2
      Metric: 5, Bidirectional

admin@J2300-1> 
[edit]
  6. Inspect the Router LSA of the router on the other side of your interface that was defined as a point-to-point link
    7. admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.3 detail    

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router   10.0.0.3         10.0.0.3         0x8000002a  1023  0x22 0x8a09  84
  bits 0x1, link count 5
  id 10.0.0.1, data 10.0.13.3, Type PointToPoint (1)
    Topology count: 0, Default metric: 5
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 5
  id 10.0.34.4, data 10.0.34.3, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.35.5, data 10.0.35.3, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.0.3, data 255.255.255.255, Type Stub (3)
    Topology count: 0, Default metric: 0
  Topology default (ID 0)
    Type: Transit, Node ID: 10.0.35.5
      Metric: 5, Bidirectional
    Type: Transit, Node ID: 10.0.34.4
      Metric: 5, Bidirectional
    Type: PointToPoint, Node ID: 10.0.0.1
      Metric: 5, Bidirectional

admin@J2300-1>
  7. Compare the LSA ID and the data for the point-to-point link
    8. admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.1 detail | match PointToPoint     
  id 10.0.0.3, data 10.0.13.1, Type PointToPoint (1)
    Type: PointToPoint, Node ID: 10.0.0.3

admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.3 detail | match PointToPoint    
  id 10.0.0.1, data 10.0.13.3, Type PointToPoint (1)
    Type: PointToPoint, Node ID: 10.0.0.1

admin@J2300-1> 
[edit]
  8. Inspect the stub advertisement that corresponds to the IP addressing on your point-to-point link for your point-to-point link
    9. admin@J2300-1>  show ospf database area 0 router lsa-id 10.0.0.1 detail | find 10.0.13.0           
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 5
  id 10.0.0.1, data 255.255.255.255, Type Stub (3)
    Topology count: 0, Default metric: 0
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.0.0.3
      Metric: 5, Bidirectional
    Type: Transit, Node ID: 10.0.12.2
      Metric: 5, Bidirectional

admin@J2300-1>
  9. Compare this advertisement to your neighbors for the same stub network
    10. admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.3 detail | find 10.0.13.0    
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 5
  id 10.0.34.4, data 10.0.34.3, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.35.5, data 10.0.35.3, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.0.3, data 255.255.255.255, Type Stub (3)
    Topology count: 0, Default metric: 0
  Topology default (ID 0)
    Type: Transit, Node ID: 10.0.35.5
      Metric: 5, Bidirectional
    Type: Transit, Node ID: 10.0.34.4
      Metric: 5, Bidirectional
    Type: PointToPoint, Node ID: 10.0.0.1
      Metric: 5, Bidirectional

admin@J2300-1>
  10. Add your router number to the metric on your point-to-point link and reinspect your router LSA
    11. admin@J2300-1> edit       
Entering configuration mode

[edit]
admin@J2300-1# set protocols ospf area 0 interface fxp1.12 metric 6 

admin@J2300-1# commit and-quit 
commit complete
Exiting configuration mode

admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.1 detail                     

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x8000004b    87  0x22 0xa17c  72
  bits 0x1, link count 4
  id 10.0.12.2, data 10.0.12.1, Type Transit (2)
    Topology count: 0, Default metric: 6
  id 10.0.0.3, data 10.0.13.1, Type PointToPoint (1)
    Topology count: 0, Default metric: 5
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 5
  id 10.0.0.1, data 255.255.255.255, Type Stub (3)
    Topology count: 0, Default metric: 0
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.0.0.3
      Metric: 5, Bidirectional
    Type: Transit, Node ID: 10.0.12.2
      Metric: 6, Bidirectional

admin@J2300-1>
  11. Compare this to your neighbors router LSA for the point-to-point network
    12. admin@J2300-1> show ospf database area 0 router lsa-id 10.0.0.3 detail    

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router   10.0.0.3         10.0.0.3         0x8000002a  1387  0x22 0x8a09  84
  bits 0x1, link count 5
  id 10.0.0.1, data 10.0.13.3, Type PointToPoint (1)
    Topology count: 0, Default metric: 5
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 5
  id 10.0.34.4, data 10.0.34.3, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.35.5, data 10.0.35.3, Type Transit (2)
    Topology count: 0, Default metric: 5
  id 10.0.0.3, data 255.255.255.255, Type Stub (3)
    Topology count: 0, Default metric: 0
  Topology default (ID 0)
    Type: Transit, Node ID: 10.0.35.5
      Metric: 5, Bidirectional
    Type: Transit, Node ID: 10.0.34.4
      Metric: 5, Bidirectional
    Type: PointToPoint, Node ID: 10.0.0.1
      Metric: 5, Bidirectional

admin@J2300-1>
  12. Inspect the your router LSAs for area 0.0.0.1, area 0.0.0.2 or area 0.0.0.3 (depending on which area your connected into)
    13. admin@J2300-1> show ospf database area 1 router detail                    

    OSPF database, Area 0.0.0.1
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Router  *10.0.0.1         10.0.0.1         0x8000001c   170  0x22 0x894f  36
  bits 0x1, link count 1
  id 10.1.111.101, data 10.1.111.1, Type Transit (2)
    Topology count: 0, Default metric: 2500
  Topology default (ID 0)
    Type: Transit, Node ID: 10.1.111.101
      Metric: 2500, Bidirectional
Router   10.0.0.3         10.0.0.3         0x80000007  2838  0x22 0x88a   36
  bits 0x1, link count 1
  id 10.1.123.102, data 10.1.123.3, Type Transit (2)
    Topology count: 0, Default metric: 10
  Topology default (ID 0)
    Type: Transit, Node ID: 10.1.123.102
      Metric: 10, Bidirectional
Router   10.1.0.1         10.1.0.1         0x80000022  2056  0x22 0xcb8a  60
  bits 0x2, link count 3
  id 10.1.111.101, data 10.1.111.101, Type Transit (2)
    Topology count: 0, Default metric: 10
  id 10.1.0.4, data 10.1.14.101, Type PointToPoint (1)
    Topology count: 0, Default metric: 10
  id 10.1.14.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 10
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.1.0.4
      Metric: 10, Bidirectional
    Type: Transit, Node ID: 10.1.111.101
      Metric: 10, Bidirectional
Router   10.1.0.2         10.1.0.2         0x8000001b  2059  0x22 0xf43c  60
  bits 0x0, link count 3
  id 10.1.123.102, data 10.1.123.102, Type Transit (2)
    Topology count: 0, Default metric: 10
  id 10.1.0.3, data 10.1.23.102, Type PointToPoint (1)
    Topology count: 0, Default metric: 10
  id 10.1.23.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 10
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.1.0.3
      Metric: 10, Bidirectional
    Type: Transit, Node ID: 10.1.123.102
      Metric: 10, Bidirectional
Router   10.1.0.3         10.1.0.3         0x80000018  2058  0x22 0x7da4  72
  bits 0x0, link count 4
  id 10.1.0.2, data 10.1.23.103, Type PointToPoint (1)
    Topology count: 0, Default metric: 10
  id 10.1.23.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 10
  id 10.1.0.4, data 10.1.34.103, Type PointToPoint (1)
    Topology count: 0, Default metric: 10
  id 10.1.34.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 10
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.1.0.4
      Metric: 10, Bidirectional
    Type: PointToPoint, Node ID: 10.1.0.2
      Metric: 10, Bidirectional
Router   10.1.0.4         10.1.0.4         0x8000001a  2057  0x22 0x4ae5  72
  bits 0x0, link count 4
  id 10.1.0.3, data 10.1.34.104, Type PointToPoint (1)
    Topology count: 0, Default metric: 10
  id 10.1.34.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 10
  id 10.1.0.1, data 10.1.14.104, Type PointToPoint (1)
    Topology count: 0, Default metric: 10
  id 10.1.14.0, data 255.255.255.0, Type Stub (3)
    Topology count: 0, Default metric: 10
  Topology default (ID 0)
    Type: PointToPoint, Node ID: 10.1.0.1
      Metric: 10, Bidirectional
    Type: PointToPoint, Node ID: 10.1.0.3
      Metric: 10, Bidirectional

admin@J2300-1>
  13. Which router is injecting external routing information into the area?

    14. Look for the E Bit set, corresponds to bit position 2, or 0x2 in Hex -- thus the 10.1.0.1 router injecting external routing information 

    admin@J2300-1> show ospf database area 1 router detail | match "(^Router|bits)"                     
Router  *10.0.0.1         10.0.0.1         0x8000001c   258  0x22 0x894f  36
  bits 0x1, link count 1
Router   10.0.0.3         10.0.0.3         0x80000008   102  0x22 0x68b   36
  bits 0x1, link count 1
Router   10.1.0.1         10.1.0.1         0x80000022  2144  0x22 0xcb8a  60
  bits 0x2, link count 3
Router   10.1.0.2         10.1.0.2         0x8000001b  2147  0x22 0xf43c  60
  bits 0x0, link count 3
Router   10.1.0.3         10.1.0.3         0x80000018  2146  0x22 0x7da4  72
  bits 0x0, link count 4
Router   10.1.0.4         10.1.0.4         0x8000001a  2145  0x22 0x4ae5  72
  bits 0x0, link count 4

admin@J2300-1>
  14. Which routers are serving as ABRs for the area?

    15. Look for the B Bit set, corresponds to bit position 1, or 0x2 in Hex -- thus the 10.0.1 and 10.0.0.3 routers are ABRs. Note that if a router was both an ABR, and injecting external routing information it would set both bits (0x03)

  15. Change the metric on your point-to-point interface back to 5
    16. admin@J2300-1> edit 
Entering configuration mode

[edit]
admin@J2300-1# rollback 1 
load complete

[edit]
admin@J2300-1# show | compare    
[edit protocols ospf area 0.0.0.0 interface fxp1.12]
-     metric 6;
+     metric 5;

[edit]
admin@J2300-1# commit and-quit 
commit complete
Exiting configuration mode

admin@J2300-1>