Screen OS

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  • 1.  OSPF external LSA in ScreenOS

    Posted 01-31-2009 02:47



    Hi all,


    Does anyone have an idea why ScreenOS (v5.1.0r1.0, NS-204) doesn't install an LSA type 5 as a route in a local routing table when shows it in ospf database and floods it to neighbors.




    The scheme is like following:


     {static route}




    [cisco router]





    |                 |

    [SSG-1]          [SSG-2]


    Form top to down: NS-1 generates an external LSA reditributing, cisco router proceeds it normally, installs it in its table and floods to NS-204. NS-204 sees the LSA, flods it to SSG boxes but doesn't install it to its own routing table. All this is in a single area 0.


    Some more techical explanation:





    NS-1-> get vr trust protocol ospf config
    VR: trust-vr RouterId:
    set protocol ospf
    set enable
    set reject-default-route
    set protocol ospf
    set redistribute route-map "rmap1" protocol static
    set interface ethernet1 protocol ospf area
    [... let's skip interfaces
    config ...]

    Route map looks like:

    set route-map name "rmap1" permit 10
    set match ip 1
    set next-hop
    set tag
    access list 1 permites




    cisco-router#sh ip route ospf | i
    O E1 [110/11] via, 00:07:14, Ethernet0/1

    cisco-router#show ip ospf database external

                OSPF Router with ID ( (Process ID 100)

                    Type-5 AS External Link States

      Routing Bit Set on this LSA
      LS age: 1265
      Options: (No TOS-capability, DC)
      LS Type: AS External Link
      Link State ID: (External Network Number )
      Advertising Router:
      LS Seq Number: 80000016
      Checksum: 0x30E6
      Length: 36
      Network Mask: /24
            Metric Type: 1 (Comparable directly to link state metric)
            TOS: 0
            Metric: 1
            Forward Address:
            External Route Tag: 2886795520




    NS-204-> get vr trust protocol ospf config
    VR: trust-vr RouterId:
    set protocol ospf
    set enable
    set advertise-def-route metric 50 metric-type 2
    set reject-default-route
    [... interfaces ...]
    NS-204-> get vr trust pro o data detail ext link-state-id
    VR: trust-vr RouterId:
                            AS External LSA(s)
    Age:  3600
    Seq Number: 0x80000017
    Checksum: 0x2ee7
    Advertising Router:
    Link State ID:
    Length: 36
    Options:   Extern     DC
    Network Mask:
                    Metric Type: 1
                    TOS: 0
                    Metric: 1
                    Forward Address:
                    External Route Tag: -1408171776
    NS-204-> get vr trust route pro o | i




    ssg-1-> get route pro o | i
    * 294       tunnel.2  E1   60     22     Root

     The LSA itself looks here just the same as on cisco-router and NS-204, so there is no need to show it once again.



    Kind regards,



  • 2.  RE: OSPF external LSA in ScreenOS
    Best Answer

    Posted 01-31-2009 03:39



    Just upgraded NS-204 to 5.4.0r12.0. 


    NS-204-> get route protocol ospf | i
    *  41           eth4  E1   60     12     Root




    It wasn't so easy due to quite heavy work the box does in production environment. I also thought it might me some explanation based on OSPF theory in which I'm not a guru.


    I'll keep this thread, if someone once bump into this issue, it might be useful for him.