OSPF- Why learnt routes are LSA5

[srikanth ath]

Hello Experts,

We have three sites among one is the datacentre. these  sites are running with dynamic routing protocol as OSPF. and they are configured as ospf  backbone area i.e area 0.        

Site1----Area0-----Datacentre----Area0-----Site2

My question is I see the routes learnt from data centre in the ospf database as  LSA-5. but my datacentre  and Site2 doesnt have any external routing protocol configured nor redistributed but, only static routes are redistributed in both.

Y it is showing the learnt routes are of LSA5 from Datacentre.

      Type-5 AS External Link States

Link ID         ADV Router     Age         Seq#       Checksum Tag

10.0.0.0       10.24.202.10     1577       0x8000C7B2 0x002CA7 13

10.0.0.0       10.24.254.220   1112       0x80008CDD 0x00E6EA 13

10.0.109.0     10.24.202.10     1577       0x80004686 0x0055BE 13

10.0.109.0     10.24.254.220  1112       0x80000BDF 0x00B330 13

10.0.126.252   10.24.202.10     1577       0x8000C257 0x00A018 13

10.0.126.252   110.24.254.220  1112       0x80008CDA 0x009BBD 13

10.0.127.235   10.24.202.10     1577       0x8000633E 0x0090B0 13

10.0.127.235   10.24.254.220   1112       0x80006334 0x000435 13

10.0.127.236   10.24.254.220    1577       0x80006336 0x0096B1 13

Thanks,

Srikanth

[Harold Ritter]

Hi Srikanth,

This is normal behavior. Static routes redistributed in OSPF should be seen as external routes (LSA type 5).

Regards

[srikanth ath]

So some of them are not static routes but just advertised with the network command.... so even these are in LSA5..what could be the reason?

[Harold Ritter]

Srikanth,

The network statement should not generate type 5 LSA's. Is it possible that you are doing "redistribute connected"?

Regards

[Rolf Fischer]

Hello  Srikanth,

so you have Site1, Site2 and DC in OSPF Area 0.

Is that Area 0 continuous, including the (WAN?) links which interconnect them?

If not, your Area 0 is partitioned and if the WAN service is a MPLS VPN, the type of the inserted remote OSPF routes depend on you service provider's setup:

• Domain IDs (default: OSPF process ID) do not match:  External (LSA Type-5)
• Domain IDs do match but no Sham Link: Inter-Area (LSA Type-3)
• Sham Link (OSPF "Superbackbone"): Intra-Area (LSA Types 1 and 2)

Hope that helps

Rolf