WALKTHROUGH: Network 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. How many network LSAs are present in the 101.101.101.101 area
    2. admin@J2300-1> show ospf database network area 101.101.101.101 summary  
Area 101.101.101.101:
   1 Network LSAs

admin@J2300-1>
  2. Examine the network LSA in the 101.101.101.101 area
    3. admin@J2300-1> show ospf database network area 101.101.101.101 detail       

    OSPF database, Area 101.101.101.101
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Network  10.101.0.10      10.10.10.10      0x80000010  2503  0x22 0xce2d  52
  mask 255.255.255.0
  attached router 10.10.10.10
  attached router 10.0.0.6
  attached router 10.0.0.5
  attached router 10.0.0.4
  attached router 10.0.0.3
  attached router 10.0.0.2
  attached router 10.0.0.1
  Topology default (ID 0)
    Type: Transit, Node ID: 10.0.0.1
      Metric: 0, Bidirectional
    Type: Transit, Node ID: 10.0.0.2
      Metric: 0, Bidirectional
    Type: Transit, Node ID: 10.0.0.3
      Metric: 0, Bidirectional
    Type: Transit, Node ID: 10.0.0.4
      Metric: 0, Bidirectional
    Type: Transit, Node ID: 10.0.0.5
      Metric: 0, Bidirectional
    Type: Transit, Node ID: 10.0.0.6    
      Metric: 0, Bidirectional
    Type: Transit, Node ID: 10.10.10.10
      Metric: 0, Bidirectional

admin@J2300-1> 
[edit]
  3. How many routers are attached to the network
    4. admin@J2300-1> show ospf database network area 101.101.101.101 detail | match "attached router" | count                
Count: 7 lines

admin@J2300-1>
  4. Who is the DR and the BDR for the network segment
    5. admin@J2300-1> show ospf interface fe-0/0/1.101 
Interface           State   Area            DR ID           BDR ID          Nbrs
fe-0/0/1.101        BDR     101.101.101.101 10.10.10.10     10.0.0.1           6

admin@J2300-1>
  5. Who is originating the network LSA?
    6. admin@J2300-1> show ospf database network area 101.101.101.101           

    OSPF database, Area 101.101.101.101
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Network  10.101.0.10      10.10.10.10      0x80000011   411  0x22 0xcc2e  52

admin@J2300-1>

    The Advertising Router 10.10.10.10 is originating the LSA, same Router ID as the DR.

  6. Examine the network LSAs for the backbone area
    7. admin@J2300-1> show ospf database network area 0 

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Network *10.0.12.1        10.0.0.1         0x80000006  2415  0x22 0xfefc  32
Network  10.0.34.3        10.0.0.3         0x80000003  1460  0x22 0x22be  32
Network  10.0.35.5        10.0.0.5         0x80000003  2408  0x22 0xfcdd  32
Network  10.0.46.4        10.0.0.4         0x80000003  1210  0x22 0xb31c  32

admin@J2300-1>
  7. How many network LSAs are present?
    8. admin@J2300-1> show ospf database network area 0 summary 
Area 0.0.0.0:
   4 Network LSAs

admin@J2300-1>
  8. How many attached routers are present in the network LSAs on the backbone?
    9. admin@J2300-1> show ospf database network area 0 lsa-id 10.0.12.1 detail | match "attached router" | count
Count: 2 lines

admin@J2300-1> show ospf database network area 0 lsa-id 10.0.34.3 detail | match "attached router" | count
Count: 2 lines

admin@J2300-1> show ospf database network area 0 lsa-id 10.0.35.5 detail | match "attached router" | count
Count: 2 lines

admin@J2300-1> show ospf database network area 0 lsa-id 10.0.46.4 detail | match "attached router" | count
Count: 2 lines
  9. Examine a network LSA for a network segment your router is connected to and locate the reference to the network segment in your Router LSA your router is generating
    10. admin@J2300-1> show ospf database network lsa-id 10.0.12.1 detail 

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Network *10.0.12.1        10.0.0.1         0x80000006  2745  0x22 0xfefc  32
  mask 255.255.255.0
  attached router 10.0.0.1
  attached router 10.0.0.2
  Topology default (ID 0)
    Type: Transit, Node ID: 10.0.0.2
      Metric: 0, Bidirectional
    Type: Transit, Node ID: 10.0.0.1
      Metric: 0, Bidirectional

admin@J2300-1> show ospf database router area 0 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         0x8000000e  2290  0x22 0xff5d  72
  bits 0x1, link count 4
  id 10.0.12.1, 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: 10.0.12.1
      Metric: 5, Bidirectional

admin@J2300-1> show ospf database router area 0 lsa-id 10.0.0.1 detail | find 10.0.12.1         
  id 10.0.12.1, data 10.0.12.1, Type Transit (2)
    Topology count: 0, Default metric: 5
  10. Note the metric of the link as reported in the Router LSA vice the Metric of the link reported in the Network LSA
    11. admin@J2300-1> show ospf database router area 0 lsa-id 10.0.0.1 detail | find 10.0.12.1         
  id 10.0.12.1, data 10.0.12.1, Type Transit (2)
    Topology count: 0, Default metric: 5

admin@J2300-1> show ospf database network lsa-id 10.0.12.1 detail | match metric                
      Metric: 0, Bidirectional
      Metric: 0, Bidirectional

admin@J2300-1>
  11. Which LSA is announcing IP addressing and subnet information for the network segment?
    12. admin@J2300-1> show ospf database network lsa-id 10.0.12.1 detail               

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 
Network *10.0.12.1        10.0.0.1         0x80000007   206  0x22 0xfcfd  32
  mask 255.255.255.0
  attached router 10.0.0.1
  attached router 10.0.0.2
  Topology default (ID 0)
    Type: Transit, Node ID: 10.0.0.2
      Metric: 0, Bidirectional
    Type: Transit, Node ID: 10.0.0.1
      Metric: 0, Bidirectional
  12. Eliminate all of the unnecessary network LSAs on the backbone
    13. admin@J2300-1> edit                                                  
Entering configuration mode

[edit]
admin@J2300-1# edit protocols ospf area 0           

[edit protocols ospf area 0.0.0.0]
admin@J2300-1# set interface fxp1.12 interface-type p2p 

[edit protocols ospf area 0.0.0.0]
admin@J2300-1# set interface fxp1.13 interface-type p2p    

[edit protocols ospf area 0.0.0.0]
admin@J2300-1# commit 
commit complete

[edit protocols ospf area 0.0.0.0]
admin@J2300-1#
  13. After all routers are finished eliminating the backbone area Network LSAs, check and see how many are network LSAs are still present in the backbone area
    14. admin@J2300-1> show ospf database area 0 network 

admin@J2300-1>
  14. Again, examine your router's Router LSA and see if you can find a reference to using the network segment as a transit network
    15. admin@J2300-1> show ospf database router area 0 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         0x80000010   204  0x22 0x70cb  84
  bits 0x1, link count 5
  id 10.0.0.2, data 10.0.12.1, Type PointToPoint (1)
    Topology count: 0, Default metric: 5
  id 10.0.12.0, data 255.255.255.0, Type Stub (3)
    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: PointToPoint, Node ID: 10.0.0.2
      Metric: 5, Bidirectional

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

admin@J2300-1>
  15. Check for a stub link announcing the IP subnet in your Router LSA
    16. admin@J2300-1> show ospf database router area 0 lsa-id 10.0.0.1 detail | match stub               
  id 10.0.12.0, data 255.255.255.0, Type Stub (3)
  id 10.0.13.0, data 255.255.255.0, Type Stub (3)
  id 10.0.0.1, data 255.255.255.255, Type Stub (3)

admin@J2300-1>