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Which router generates LSA Type 4?

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  • 1.  Which router generates LSA Type 4?

    Posted 01-16-2020 22:20

    If ABR connects area 0 and area 2 (NSSA), does this router generates LSA Type 4 into area 0 ?

    thanks !!



  • 2.  RE: Which router generates LSA Type 4?

     
    Posted 01-16-2020 22:53

     

    It would if it needs to! Here is perfect example:

    https://packetlife.net/blog/2008/apr/21/where-are-type-4-lsas-generated/

     

     

     

     



  • 3.  RE: Which router generates LSA Type 4?

    Posted 01-17-2020 08:09

    I did read that link (paketlife) before.  My question is:

    Does router B generates LSA type 4 ?  Based on my understanding of that post, only Router C generates LSA type 4.  Anything I missed ?

     

    thanks !!



  • 4.  RE: Which router generates LSA Type 4?

     
    Posted 01-17-2020 06:36

    Yes. 


    Check

    https://tools.ietf.org/html/rfc2328#page-117

     

    12.1.3. LS type 

    Table 15: OSPF link state advertisements (LSAs). >>This tells you basically type 3 and type 4 are the same

     

    12.1.5. Advertising Router
    Summary-LSAs originated by area border routers.

     



  • 5.  RE: Which router generates LSA Type 4?

    Posted 01-17-2020 08:21

    OSPF-LSA.JPG

    Should vMX6 generates LSA type 4 ?  When I capture the packets, I did not see Type 4 on that router. I only see Type 4 on vMX5.  I like to confirm it.

    In my training material, I saw Type 4 in Area 0, but I could not do that in my lab.

    On vMX5, Type 4 only  shows in Area 2, not Area 0.

    root@vMX5# run show ospf database asbrsummary extensive
    
        OSPF database, Area 0.0.0.2
     Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
    ASBRSum *6.6.6.6          5.5.5.5          0x80000001    43  0x22 0xed1f  28
      mask 0.0.0.0
      Topology default (ID 0) -> Metric: 3
      Gen timer 00:49:17
      Aging timer 00:59:17
      Installed 00:00:43 ago, expires in 00:59:17, sent 00:00:11 ago
      Last changed 00:00:43 ago, Change count: 1, Ours
    On vMX6, no Type 4 LSA
    root@vMX6# run show ospf route | match Ext2
    10.10.10.10/32     Ext2  Network    IP            2 ge-0/0/0.0    192.168.30.9
    140.142.41.0/24    Ext2  Network    IP            2 ge-0/0/0.0    192.168.30.9
    root@vMX6# run show ospf database asbrsummary extensive
    
    [edit]
    
    

    thanks for coaching !!



  • 6.  RE: Which router generates LSA Type 4?
    Best Answer

     
    Posted 01-17-2020 09:28

    Hi 

     

    Your understanding is almost correct. However, I believe the reason you are not seeing VMX6 sending type 4 is because your area 3 is defined as NSSA. Try to define area 3 as normal area. You should see a difference 



  • 7.  RE: Which router generates LSA Type 4?

    Posted 01-17-2020 10:52

    If I define Area 3 to be normal area, in my understanding, only Type 3 is generated, not Type 4, as Type 4 is about how to reach ASBR, right ?



  • 8.  RE: Which router generates LSA Type 4?

    Posted 01-17-2020 16:43

    in theory if  an abr receives a LSA type 1 with the E bit set and receives an LSA type 5, it will originate both LSA type 3 and type 4 into the adjacent area, becoming a psuedo asbr.

     

    so the LSA Type 4 is created by the ABR with an LSA type 1 with the E-bit set by the ASBR



  • 9.  RE: Which router generates LSA Type 4?

    Posted 01-17-2020 19:23
    root@vMX6# run show ospf database
    
        OSPF database, Area 0.0.0.0
     Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
    Router   1.1.1.1          1.1.1.1          0x800000bb   706  0x22 0x4c57  60
    Router   2.2.2.2          2.2.2.2          0x800000c3  2008  0x22 0x675a  72
    Router   3.3.3.3          3.3.3.3          0x800000bc  1615  0x22 0x6d07  72
    Router   4.4.4.4          4.4.4.4          0x800000a6  1710  0x22 0xe522  48
    Router   5.5.5.5          5.5.5.5          0x80000021  1296  0x22 0xeb7f  48
    Router  *6.6.6.6          6.6.6.6          0x8000009a  2990  0x22 0xf9d3  48
    Network  10.10.10.4       4.4.4.4          0x8000009c  1210  0x22 0xbea8  32
    Network  10.10.20.5       5.5.5.5          0x8000001d  1153  0x22 0x7b54  32
    Network *10.10.30.6       6.6.6.6          0x8000009a  2561  0x22 0x3efc  32
    Network  20.20.10.2       2.2.2.2          0x800000b5   667  0x22 0x9dae  32
    Network  20.20.20.3       3.3.3.3          0x8000009e   154  0x22 0x89c2  32
    Summary  7.7.7.7          4.4.4.4          0x8000009d  2710  0x22 0x9ed4  28
    Summary  8.8.8.8          5.5.5.5          0x8000001d  1582  0x22 0x5398  28
    Summary  192.168.10.0     4.4.4.4          0x800000a2  2210  0x22 0x5dc8  28
    Summary  192.168.20.0     5.5.5.5          0x80000022  1439  0x22 0xd1c6  28
    Summary *192.168.30.0     6.6.6.6          0x8000009f   418  0x22 0x4ac2  28
    
        OSPF database, Area 0.0.0.3
     Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
    Router  *6.6.6.6          6.6.6.6          0x800000a2  1704  0x20 0x63c   36
    Router   172.16.10.9      172.16.10.9      0x800000a2  2200  0x20 0x9937  36
    Network  192.168.30.9     172.16.10.9      0x8000009d  1450  0x20 0xde87  32
    NSSA    *0.0.0.0          6.6.6.6          0x80000095  2133  0x20 0x676   36
    NSSA     10.10.10.10      172.16.10.9      0x80000097   700  0x28 0xcabe  36
    NSSA     140.142.41.0     172.16.10.9      0x80000096  2950  0x28 0x46a   36
        OSPF AS SCOPE link state database
     Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
    Extern  *10.10.10.10      6.6.6.6          0x80000099  1275  0x22 0x97af  36
    Extern  *140.142.41.0     6.6.6.6          0x80000099   847  0x22 0xce5c  36
    
    [edit]
    

    This is ospf database for vMX6. Seems no Type 4. Should it have Type 4 ?  That is what I am not sure.

    The following is captured LS Update packet.

    OSPF-LSA-2.JPG



  • 10.  RE: Which router generates LSA Type 4?

    Posted 01-17-2020 19:32

    thanks for your input.



  • 11.  RE: Which router generates LSA Type 4?

    Posted 01-17-2020 23:03

    thanks a lot !   You are right, after I removed NSSA, type 4 shows up.



  • 12.  RE: Which router generates LSA Type 4?

    Posted 01-17-2020 21:22

    thanks for all for taking a look at this and your help. 

    I did it in the Cisco and verify all the ABR routers generates type 4 if it connects to NSSA.

    cisco-lsa-type-4-2.JPG

    On R5

    R5#show ip ospf database asbr-summary
    
                OSPF Router with ID (192.168.20.5) (Process ID 10)
    
                    Summary ASB Link States (Area 0)
    
      LS age: 254
      Options: (No TOS-capability, DC, Upward)
      LS Type: Summary Links(AS Boundary Router)
      Link State ID: 8.8.8.8 (AS Boundary Router address)
      Advertising Router: 192.168.20.5
      LS Seq Number: 80000001
      Checksum: 0xB7D7
      Length: 28
      Network Mask: /0
            MTID: 0         Metric: 10
    

    Packet captured

    cisco-lsa-type-4-1.JPG

    I can't see Type 4 on vMX6, it might be vMX issue.  I will test on the physical devices.

     

    thanks again for all !!