OSPF link won't show in LSDB database command

[Amafsha1]

Hello all,

I have a simple topology where a Router(R1) has three interfaces

g0/0 - 10.10.10.6 to other OSPF neighbor (area 0) (to R2 router)

g0/1 - to /24 network (networkd in OSPF area 0) 172.28.6.0/24

g0/2 - to /24 Network (networkd in OSPF area 0) 172.28.7.0/24

why is it when I advertise the 2 networks g0/1 and g0/2 in OSPF, they show up in the route table as O Routes for other OSPF routers but they don't show up in their LSDB?

router ospf 1

network 172.28.6.0 0.0.0.255 area 0

network 172.28.7.0 0.0.0.255 area 0

so I see the routes in "show ip route" of R2 I also see them in "show ip route ospf" of R2.  I also see them in the "sh ip ospf database router" of R2

but when I input the "show IP ospf database" command, I don't see these links.  the only way I can see them is if I use the "redist connected subnets" command, then the other routers will show them as Type 5 external routes.  

When I input the necessary verfication commands in R2, I get the following:

R1 router-id 20.20.20.6

R2 #show IP route 
O 172.16.24.0 [110/12] via 10.10.10.6, 00:52:03, GigabitEthernet0/0
O 172.16.25.0 [110/12] via 10.10.10.6, 00:52:03, GigabitEthernet0/0

R2# show ip ospf datab router

LS age: 1082
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 20.20.20.6
Advertising Router: 20.20.20.6
LS Seq Number: 8000001B

Link connected to: a Stub Network
(Link ID) Network/subnet number: 172.28.6.0
(Link Data) Network Mask: 255.255.255.0
Number of MTID metrics: 0
TOS 0 Metrics: 1

Link connected to: a Stub Network
(Link ID) Network/subnet number: 172.28.7.0
(Link Data) Network Mask: 255.255.255.0
Number of MTID metrics: 0
TOS 0 Metrics: 1

but when I type in "show ip route ospf dat", I don't see anything about the 172.28.6 or .7 network in R2

Why is this happening?   obviously it needs to know about the link in order for the ip route table to have the route correct?

It's funny because people usually ask, "why does a route in the LSDB not show in the IP route table", but for me the question seems to be the opposite. 

[Giuseppe Larosa · Accepted solution]

Hello @Amafsha1 ,

an OSPF router generates an OSPF Router LSA for each area it is member of that includes the list of all interfaces that are active in OSPF in that area.

So what you see is really normal.

You see specific per IP prefix entries in LSDB when you use redistribute connected but when you advertise the subnets as external routes.

When you advertise the networks as internal routes in area 0 , there is a single entry in LSDB that is the router LSA and the router LSA has an ID = R1 OSPF RID. This is normal, but the detail of the router LSA lists the additional interfaces in area 0 as stub networks (because there are no OSPF neighbors out those interfaces).

See from your own post:

R2# show ip ospf database router

LS age: 1082
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 20.20.20.6    =    R1 OSPF RID
Advertising Router: 20.20.20.6   =  R1 OSPF RID
LS Seq Number: 8000001B

Link connected to: a Stub Network
(Link ID) Network/subnet number: 172.28.6.0
(Link Data) Network Mask: 255.255.255.0
Number of MTID metrics: 0
TOS 0 Metrics: 1

Link connected to: a Stub Network
(Link ID) Network/subnet number: 172.28.7.0
(Link Data) Network Mask: 255.255.255.0
Number of MTID metrics: 0
TOS 0 Metrics: 1

So it is true there is no OSPF data structure with an LSA ID equal to that of one of the two subnets 172.28.6.0/24 and 172.28.7.0/24 but both are listed in the R1's Router LSA as member links of area0 in R1. so it is not correct to say that they are not present in the OSPF database.

Again, what you see is normal it is the way that OSPF works.

If R1 would be an ABR between area 0 and area 11, R1 would generate two OSPF Router LSA one for area 0 and one for area 11 both with the same LSA ID = R1 OSPF RID but with different content (the different subsets of interfaces in area  0 and area 11 respectively)

Hope to help

Giuseppe