Redistribute connected generating Type 5 LSA

When I issue the redistribute connect command under the OSPF process, is the router generating Type 5 LSAs for connectedlinks that are already running OSPF? The reason that I ask is because I have a router (R4) that is redistributing connected but this router only has a loopback and one link and both are already running OSPF. If I look at the OSPF database for this area I do not see the Type 5 LSA; however, the ABR is generating a Type 4 LSA for the ASBR R4. 

 

If R4 is not generating a Type 5 LSA for his connected links, then how does the ABR know to generate a Type 4 LSA? If R4 is generating a Type 5 LSA, shouldn't I see this LSA in the database even if it is not being used because there is a "better" LSA that describes this prefix?

 

Thanks!

 

Drew

Comments

  • this maybe bug in IOU; connected routes are not redistiruted.

    see http://ieoc.com/forums/t/30875.aspx

  • JoeMJoeM ✭✭✭

    When I issue the redistribute connect command under the OSPF process, is the router generating Type 5 LSAs for connectedlinks that are already running OSPF? The reason that I ask is because I have a router (R4) that is redistributing connected but this router only has a loopback and one link and both are already running OSPF.

     I believe that a network advertisement trumps a redistribution of the same route.

    What are trying to do?  Advertise and Redistribute the same interfaces?

     

     

    What type of area is this?  Within an NSSA area, it would be a Type-7 route.  Outside an NSSA area it would be seen as a type-5.

    But then again, you say that the interfaces are already advertised into the database (lsa type-1 or type-3)

     

     

    If R4 is not generating a Type 5 LSA for his connected links, then how does the ABR know to generate a Type 4 LSA?

    I always find this article interesting. It may explain your situation (lsa type-4 but no type-5).

                     Where are type 4 LSA's generated? - Packetlife

     

     

    I say yes, if a router truly s generating Type 5 LSA.  But that was the original question, if a type-5 is being generated or not.


    Post your OSPF configs (only ospf).  It would be interesting to look at your setup.

     

  • JoeMJoeM ✭✭✭

    I created a mini-lab to verify what I was thinking.   

                   R1 (Area 12) R2 (Area 0) R3 (Area 34) R4

    R1 is the redistributing router (ASBR in Area 12).  Check the databases on R3 and R4.

     

    Network advertisements do trump redundant redistribution of the same route.

    So why does R3 create the Summary-ASB-Link?

    Because we have a router saying it is an ASBR.  It does not matter whether R1 has anything legitimate to redistribute.  R1 is saying it is an ASBR...so the ABR's in other Areas are dutifully preparing for it.

     

    To see this, look at your ospf database in another area.

    1.  Where in the database, are the networks that you are looking for? Under Summary Net Link States (lsa type-3 for other areas), correct? 

    2.  Now create another loopback on the same ASBR. The newly UN-advertised network will show up as LSA Type-5, as we would expect.

     

    Hope this helps.

     

  • Thank you both for your responses.

    Joe,

    In your example, how would R1 tell R2 that he is an ASBR? What I am wondering is R1 still generating a type 5 LSA and the rest of the routers in the area are just ignoring this LSA completely because they have a better LSA that describes this prefix? Or is there some other way that R1 is communicating to R2 that he is an ASBR?

     

    Thanks,

     

    Drew

  • JoeMJoeM ✭✭✭

    Or is there some other way that R1 is communicating to R2 that he is an ASBR?

    This.  It is initially done in an LS Update from the ASBR.

     

    Below is a packet capture to show the difference WITH and WITHOUT.

    Notice the Redistribution Flags:  

              Flags: 0x02 (E)   vs    Flags: 0x00

     

    WITH redistribution:

    Frame 4: 110 bytes on wire (880 bits), 110 bytes captured (880 bits)
    Ethernet II, Src: aa:bb:cc:00:01:00 (aa:bb:cc:00:01:00), Dst: 01:00:5e:00:00:05 (01:00:5e:00:00:05)
    Internet Protocol Version 4, Src: 12.12.12.1 (12.12.12.1), Dst: 224.0.0.5 (224.0.0.5)
    Open Shortest Path First
        OSPF Header
        LS Update Packet
            Number of LSAs: 1
            Router-LSA
                .000 1110 0001 0000 = LS Age (seconds): 3600
                0... .... .... .... = Do Not Age Flag: 0
                Options: 0x22 (DC, E)
                LS Type: Router-LSA (1)
                Link State ID: 11.11.11.11 (11.11.11.11)
                Advertising Router: 11.11.11.11 (11.11.11.11)
                Sequence Number: 0x8000000c
                Checksum: 0xc3a0
                Length: 48
                Flags: 0x02 (E)
                    .... .0.. = V: NO Virtual link endpoint
                    .... ..1. = E: AS boundary router
                    .... ...0 = B: NO Area border router
                Number of Links: 2
                Type: Stub     ID: 1.1.1.1         Data: 255.255.255.255 Metric: 1
                Type: Transit  ID: 12.12.12.2      Data: 12.12.12.1      Metric: 10

     

    WITHOUT redistribution:

    Frame 7: 110 bytes on wire (880 bits), 110 bytes captured (880 bits)
    Ethernet II, Src: aa:bb:cc:00:01:00 (aa:bb:cc:00:01:00), Dst: 01:00:5e:00:00:05 (01:00:5e:00:00:05)
    Internet Protocol Version 4, Src: 12.12.12.1 (12.12.12.1), Dst: 224.0.0.5 (224.0.0.5)
    Open Shortest Path First
        OSPF Header
        LS Update Packet
            Number of LSAs: 1
            Router-LSA
                .000 1110 0001 0000 = LS Age (seconds): 3600
                0... .... .... .... = Do Not Age Flag: 0
                Options: 0x22 (DC, E)
                LS Type: Router-LSA (1)
                Link State ID: 11.11.11.11 (11.11.11.11)
                Advertising Router: 11.11.11.11 (11.11.11.11)
                Sequence Number: 0x8000000f
                Checksum: 0xb7ab
                Length: 48
                Flags: 0x00
                    .... .0.. = V: NO Virtual link endpoint
                    .... ..0. = E: NO AS boundary router
                    .... ...0 = B: NO Area border router
                Number of Links: 2
                Type: Stub     ID: 1.1.1.1         Data: 255.255.255.255 Metric: 1
                Type: Transit  ID: 12.12.12.2      Data: 12.12.12.1      Metric: 10


     

  • Joe you are awesome!! Thank you so much, this is exactly what I was looking for. 

  • JoeMJoeM ✭✭✭

    Your welcome.   I learned a couple things myself by doing the packet capture.  ;-)

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