Nexus 7k not flooding ospf LSAs from nssa area

[jleszewski]

Hi,

I have a pair of Nexus 7k configured as ABRs. Problem is that one of them seems to not flood LSA received from a NSSA area into backbone area.

Topology:

     area 0

|               |

abr1------abr2

|               |      

|   nssa     |

|               |

agg1-----agg2

Devices to which these N7ks connect to via nssa area are configured identically.

Both agg1 and agg2 redistribute connected routes, which abr1 and abr2 flood into the backbone.

And while agg2 works fine, agg1 doesn't.

When running "show ip ospf database external self-originated" command on abr1 shows nothing, while the second box shows expected results (links receivced from agg2)

Configuration is very simple. no filtering,distribute-list, route-maps etc..

Anyone can tell what might be the reason for such behaviour?

best regards

Kuba

[Rolf Fischer · Accepted solution]

Hi Kuba,

the type-7 to type-5 translation is only done by the ABR with the highest RID if multiple NSSABRs exist:

R1#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface

2.2.2.2           0   FULL/  -        00:00:31    172.16.12.2     Serial0/1

3.3.3.3           0   FULL/  -        00:00:31    172.16.13.3     Serial0/0

R1#show ip ospf database external self-originate

OSPF Router with ID (1.1.1.1) (Process ID 1)

R1#

R1(config-router)#router-id 10.10.10.10

R1#clear ip ospf proc

Reset ALL OSPF processes? [no]: yes

R1#show ip ospf database external self-originate

OSPF Router with ID (10.10.10.10) (Process ID 1)

Type-5 AS External Link States

LS age: 0

Options: (No TOS-capability, DC)

LS Type: AS External Link

Link State ID: 192.168.2.0 (External Network Number )

Advertising Router: 10.10.10.10

LS Seq Number: 80000001

Checksum: 0x6F51

Length: 36

Network Mask: /24

Metric Type: 1 (Comparable directly to link state metric)

TOS: 0

Metric: 20

Forward Address: 172.16.13.3

External Route Tag: 0

http://blog.ine.com/2008/11/24/new-ospf-updates-teaser/

Hope that helps

Rolf

[jleszewski]

I get it. Thank You.