P-bit in type-7 LSA. OSPF NSSA.

[Fujitsu_cyberSOC]

Hi,

Is it possible to send OSPF LSA type-7 in a NSSA area with P-bit=1 ?

We are using PA as ASBR (just ASBR, no ABR) and redistributing some BGP route into OSPF. The prefix is send as expected as type-7 (NSSA Ext) :

admin@PA01(active)> show routing protocol bgp loc-rib | match 10.247
  Prefix             Nexthop          Peer       Weight   LocPrf Org      MED flap AS-Path
*10.247.128.0/17    10.118.112.172   peer_virtual      0      100 i/c       11    0 65333,65333,65333,65333,65333,65333,65333

admin@NIX2-PA01(active)> show routing protocol ospf dumplsdb
VIRTUAL ROUTER: GW-NIX (id 2)
  ==========
VR  Area ID         Orig RTR ID     LS ID              LSA Type             Seq Number CheckSum   Age  
...
2   0.0.0.2         0.0.0.4         10.247.128.0/17    type-7 (NSSA Ext)    0x8000002C 0x00005B44 1611 
            Options: [none]
            Mask 255.255.128.0, type 2, tos 0 metric: 1, forward 0.0.0.0, tag 0.0.0.0

But in the OSPF neighbor acting as ABR no type-7 to type-5 translation is done, so we think that P-bit must be 0 for those LSA.

VSS-coreA#sh ip ospf database nssa-external 10.247.128.0

            OSPF Router with ID (0.0.0.3) (Process ID 1)

       Type-7 AS External Link States (Area 2)

  Routing Bit Set on this LSA
  LS age: 1253
  Options: (No TOS-capability, No Type 7/5 translation, No DC)
  LS Type: AS External Link
  Link State ID: 10.247.128.0 (External Network Number )
  Advertising Router: 0.0.0.4
  LS Seq Number: 8000002D
  Checksum: 0x5945
  Length: 36
  Network Mask: /17
    Metric Type: 2 (Larger than any link state path)
    TOS: 0
    Metric: 1
    Forward Address: 0.0.0.0
    External Route Tag: 0

So far, we have tried to no avail:

- Adding the interface connected to BGP peer to OSPF as passive.

- Adding the BGP prefix 10.247.128.0/17 to OSPF NSSA Area Ext Ranges (LSA is type-7 in this case also, No Type 7/5 translation in the ABR)

- Adding the BGP prefix 10.247.128.0/17 to OSPF Area Ranges (then is send as type-5 and filtered as the area is NSSA).

Best regards,

[mrajdev · Accepted solution]

Hi,

At this time we do not have a option to set the P-bit for routes getting redistributed into NSSA OSPF area. I would suggest to please contact your sales team to request for them to put in a feature request.

Thanks