OSPF Database Question

Unanswered Question
Jan 22nd, 2009

I have a router (R1) and it advertises 19.89.12.0 through its OSPF neighbor relationship with D1 (data center router).

The route table on D1 shows R1 as the next hop for 19.89.12.0 (as expected), but the OSPF database shows 3 other routers (including itself) as the source of the OSPF database LSAs for 19.89.12.0. (see addresses in bold)

The fact that D1 shows other routers as sources for Link State Updates for 19.89.12.0 doesnt confuse me, except perhaps for the fact that it shows itself as one of the sources.

Besides that, though, what I cant figure out is why D1 doesnt also show the LSAs it's receiving from R1 for 19.89.12.0 in its database.

D1#

D1#sh ip ospf database summary 19.89.12.0

OSPF Router with ID (19.211.6.74) (Process ID 521)

Summary Net Link States (Area 0)

LS age: 1329

Options: (No TOS-capability, DC, Upward)

LS Type: Summary Links(Network)

Link State ID: 19.89.12.0 (summary Network Number)

Advertising Router: 19.211.2.16

LS Seq Number: 80000674

Checksum: 0xDCE0

Length: 28

Network Mask: /26

TOS: 0 Metric: 6586

LS age: 1716

Options: (No TOS-capability, DC, Upward)

LS Type: Summary Links(Network)

Link State ID: 19.89.12.0 (summary Network Number)

Advertising Router: 19.211.6.74

LS Seq Number: 80000673

Checksum: 0x796B

Length: 28

Network Mask: /26

TOS: 0 Metric: 6486

LS age: 1486

Options: (No TOS-capability, DC, Upward)

LS Type: Summary Links(Network)

Link State ID: 19.89.12.0 (summary Network Number)

Advertising Router: 19.211.6.90

LS Seq Number: 8000066D

Checksum: 0x7A3E

Length: 28

Network Mask: /26

TOS: 0 Metric: 6520

D1#

D1#sh ip ro 19.89.12.0

Routing entry for 19.89.12.0/26

Known via "ospf 521", distance 110, metric 6486, type intra area

Last update from 19.210.67.98 on Serial9/0/5:0, 15:07:27 ago

Routing Descriptor Blocks:

* 19.210.67.98, from 19.211.146.10, <------------------------------R1/next hop.

15:07:27 ago, via Serial9/0/5:0

Route metric is 6486, traffic share count is 1

D1#

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Giuseppe Larosa Thu, 01/22/2009 - 13:17

Hello Victor,

the route is intra area.

you should find in your database a router LSA (LSA type 1) generated by the real owner of the IP subnet.

By using the command you used you are looking for LSA type 3.

However, D1 and other routers can be ABR connecting area 0 to other areas.

So they can be authorized to generate a summary LSA type 3 LSA in order to propagate knowledge of prefix in other standard areas and stub areas (not to totally stub areas).

in what area is ser9/0/5:0 ?

Hope to help

Giuseppe

lamav Thu, 01/22/2009 - 13:25

Giuseppe:

Of course, how stupid of me. When I saw the word "summary" I wasnt thinking summary routes. I was thinking that the command will give me a summary of the OSPF database! LOL Hellooooo?? Anybody home??? LOL

Anyway, I did run the OSPF database command to see a router LSA, yet it is still not there.

D1#sh ip ospf database router 19.89.12.0

OSPF Router with ID (19.211.6.74) (Process ID 521)

D1#

D1#

D1#sh ip ospf database network 19.89.12.0

OSPF Router with ID (19.211.6.74) (Process ID 521)

D1#

Also, I think I see why D1 shows itself as a source for the 19.89.12.0 LSA. It is indeed an ABR and it is injecting summary routes into Area 0. If it werent an OSPF ABR, I would still see the network in question in D1's database, but not as a summary route, but as perhaps a router LSA. Correct?

Giuseppe Larosa Thu, 01/22/2009 - 13:41

Hello Victor,

no problem sometimes someone external sees what we are missing

the router LSA you should look for should be "named" with the router-id of the intra-area route next hop you should see it looking at (the router LSA is only one with all connected subnets in area X listed as subfields)

look at from ...

in sh ip route 10.89.12.0

Hope to help

Giuseppe

lamav Thu, 01/22/2009 - 18:42

Giuseppe:

i figured it out.

I had to execute a "sh ip ospf database 19.211.146.10" on D1. That address is the OSPF router ID of R1. Upon doing so, it will tell you the number of "links" that R1 is advertising to D1.

eccrsd6#sh ip ospf database router 19.211.146.10

OSPF Router with ID (19.211.6.74) (Process ID 521)

Router Link States (Area 200)

LS age: 130

Options: (No TOS-capability, DC)

LS Type: Router Links

Link State ID: 19.211.146.10

Advertising Router: 19.211.146.10

LS Seq Number: 8000071D

Checksum: 0xAA4A

Length: 408

Number of Links: 32

Link connected to: a Transit Network

(Link ID) Designated Router address: 19.210.146.17

(Link Data) Router Interface address: 19.210.146.17

Number of TOS metrics: 0

TOS 0 Metrics: 10

Link connected to: another Router (point-to-point)

(Link ID) Neighboring Router ID: 19.211.6.74

(Link Data) Router Interface address: 19.210.67.98

Number of TOS metrics: 0

TOS 0 Metrics: 6510

Link connected to: a Stub Network

(Link ID) Network/subnet number: 19.89.12.0

(Link Data) Network Mask: 255.255.255.192

Number of TOS metrics: 0

TOS 0 Metrics: 10

Its interesting, though. I would have thought that I could have searched the database by executing "sho ip ospf database 19.89.12.0". That address is the user network I am really interested in.

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