Technical Tip: OSPF propagation network prefix (LSA Type 1 – Router LSA)

[JohnDevNet_FTNT]

Purpose
In this scenario OSPF is running between other vendor router device and a FortiGate
192.168.1.0/24 Network is not being propagating over the network.
192.168.1.0/24 Network is attached and properly configured in 'other vendor router'. access to this device is denied.
For this case,access to the third party device is limited.

This article describes how a device which runs OSPF is propagating a Network prefix properly.

Scope
The purpose of this document is to explain how to read OSPF Link State Database to confirm what is causing this problem.
Diagram

Expectations, Requirements
Sometimes  access to other networkis are limited.
No access to 'other vendor router', so troubleshoot this problem in Fortinet network side is needed.
OSPF uses different types of LSAs (Link States Advertisements) to build a LSDB (Link State Database), which is like a map of the OSPF network topology.
These are the most common LSAs:

LSA Type 1: Router LSA.
LSA Type 2: Network LSA.
LSA Type 3: Summary LSA.
LSA Type 4: Summary ASBR LSA.
LSA Type 5: Autonomous system external LSA.
LSA Type 6: Multicast OSPF LSA.
LSA Type 7: Not-so-stubby area LSA.
LSA Type 8: External attribute LSA for BGP.

Analyze LSA Type 1 (ROUTER LSA)  for the troubleshooting:

LSA Type 1 Description:

Every router within an area will flood a type 1 router LSA within the area.

The LSA (Type 1) will list with all the directly connected links of this router.

LSA Type 1 will stays within the area .

Configuration
Other vendor configuration:

'Other vendor router', OSPF configuration seems to be properly done.

#router ospf 1

network 10.10.10.0 0.0.0.255 area 0.0.0.0
network 10.180.50.0 0.0.0.255 area 0.0.0.0
network 172.16.1.0 0.0.0.255 area 0.0.0.0
network 192.168.1.0 0.0.0.255 area 0.0.0.0

Configuration router 1:

# show router ospf

# config router ospf
     set router-id 1.1.1.1
          config area
               edit 0.0.0.0
          next
       end

# config ospf-interface
     edit "10"
          set interface "port10"
          set network-type point-to-point
     next
          edit "20"
               set interface "port1"
               set network-type point-to-point
          next
     end

# config network
     edit 10
          set prefix 10.10.10.0 255.255.255.0
     next
          edit 20
               set prefix 10.20.20.0 255.255.255.0
          next
     end

Configuration router 2:

# config router ospf
     set router-id 2.2.2.2
          config area
               edit 0.0.0.0
          next
     end

# config ospf-interface
     edit "20"
          set interface "port1"
          set network-type point-to-point
     next
end

# config network
     edit 20
          set prefix 10.20.20.0 255.255.255.0
     next
end

Verification
FortiGate verification commands:

All adjacencies are being established fine.

Router 1 :

# get router info ospf neighbor

OSPF process 0:
Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           1   Full/ -         00:00:32    10.10.10.2      port10
2.2.2.2           1   Full/ -         00:00:32    10.20.20.2      port1

Router 2:

# get router info ospf neighbor

OSPF process 0:
Neighbor ID     Pri   State           Dead Time   Address         Interface
1.1.1.1           1   Full/ -         00:00:33    10.20.20.1      port1

Routes for network 10.180.50.0/24 and network 172.16.1.0/24, are being received, and installed in router 1 and router 2.

Router 1:

# get router info routing-table ospf

10.180.50.0/24 [110/2] via 10.10.10.2, port10, 00:46:39
172.16.1.0/24 [110/2] via 10.10.10.2, port10, 00:46:39

Router 2:

# get router info routing-table ospf

10.180.50.0/24 [110/3] via 10.20.20.1, port1, 00:41:08
172.16.1.0/24 [110/3] via 10.20.20.1, port1, 00:41:08

Troubleshooting
The problem is that Network 192.168.1.0/24 is not being propagated.
Confirm if problem is in Fortinet side.

Solution:

Every Router within the area is sending a LSA Type 1.

Router 1:

# get router info ospf database brief

Router Link States (Area 0.0.0.0)
Link ID         ADV Router      Age  Seq#     CkSum Flag Link count
1.1.1.1         1.1.1.1         874  8000000f 68ed  0012 4
2.2.2.2         2.2.2.2         783  80000003 487e  0031 2
3.3.3.3         3.3.3.3         275  80000004 7084  0002 4

Details of every LSA Type 1 are shown with the command below:

# get router info ospf database router lsa

<A.B.C.D>    LSA id

LSA Type 1, contains all network prefixes attached to every router.

According to the LSA type 1 details of 3.3.3.3, the details of network 192.168.1.0/24 is not in the list.
That means that 'other vendor router', is not generating the LSA Type properly and  is not propagating network 192.168.1.0/24 properly:

# get router info ospf database router lsa 3.3.3.3
               
Router Link States (Area 0.0.0.0)
LS age: 814
Options: 0x22 (*|-|DC|-|-|-|E|-)
Flags: 0x0
LS Type: router-LSA
Link State ID: 3.3.3.3
Advertising Router: 3.3.3.3
LS Seq Number: 80000004
Checksum: 0x7084
Length: 72
Number of Links: 4
Link connected to: Stub Network
(Link ID) Network/subnet number: 172.16.1.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metric: 1
Link connected to: Stub Network
(Link ID) Network/subnet number: 10.180.50.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metric: 1
Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID: 1.1.1.1
(Link Data) Router Interface address: 10.10.10.2
 Number of TOS metrics: 0
TOS 0 Metric: 1
Link connected to: Stub Network
(Link ID) Network/subnet number: 10.10.10.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metric: 1

After checking configuration in 'other device vendor', network 192.168.1.0/24, now is into the LSA Type 1, and FortiGates now can put this network in their routing table:

# get router info ospf database router lsa 3.3.3.3

Router Link States (Area 0.0.0.0)
LS age: 6
Options: 0x22 (*|-|DC|-|-|-|E|-)
Flags: 0x0
LS Type: router-LSA
Link State ID: 3.3.3.3
Advertising Router: 3.3.3.3
LS Seq Number: 80000005
Checksum: 0x5325
Length: 84
Number of Links: 5
Link connected to: Stub Network
(Link ID) Network/subnet number: 192.168.1.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metric: 1
Link connected to: Stub Network
(Link ID) Network/subnet number: 172.16.1.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metric: 1
Link connected to: Stub Network
(Link ID) Network/subnet number: 10.180.50.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metric: 1
Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID: 1.1.1.1
(Link Data) Router Interface address: 10.10.10.2
Number of TOS metrics: 0
TOS 0 Metric: 1
Link connected to: Stub Network
(Link ID) Network/subnet number: 10.10.10.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metric: 1

Fortigate Routing table after problem solved:

Router 1:

# get router info routing-table ospf

10.180.50.0/24 [110/2] via 10.10.10.2, port10, 01:07:23
172.16.1.0/24 [110/2] via 10.10.10.2, port10, 01:07:23
192.168.1.0/24 [110/2] via 10.10.10.2, port10, 00:03:41

Router 2:

# get router info routing-table ospf

10.180.50.0/24 [110/3] via 10.20.20.1, port1, 01:01:25
172.16.1.0/24 [110/3] via 10.20.20.1, port1, 01:01:25
192.168.1.0/24 [110/3] via 10.20.20.1, port1,