1. Router LSA – This LSA is produced by every router. The LSA contains information of the router’s connected interfaces, states, neighbour router type, any known ospf routers connected to the router’s link and outgoing cost of each link. This LSA floods within its own area (intra-area flooding), hence this LSA describes intra-area route.
r1#show ip ospf database router OSPF Router with ID (1.1.1.1) (Process ID 1) Router Link States (Area 0) LS age: 265 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 1.1.1.1 Advertising Router: 1.1.1.1 LS Seq Number: 80000008 Checksum: 0xE690 Length: 48 Number of Links: 2 Link connected to: a Stub Network (Link ID) Network/subnet number: 1.1.1.1 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Transit Network (Link ID) Designated Router address: 172.30.0.1 (Link Data) Router Interface address: 172.30.0.1 Number of TOS metrics: 0 TOS 0 Metrics: 1 Routing Bit Set on this LSA LS age: 1867 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 2.2.2.2 Advertising Router: 2.2.2.2 LS Seq Number: 80000008 Checksum: 0xD98F Length: 48 Area Border Router Number of Links: 2 Link connected to: a Stub Network (Link ID) Network/subnet number: 2.2.2.2 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Transit Network (Link ID) Designated Router address: 172.30.0.1 (Link Data) Router Interface address: 172.30.0.2 Number of TOS metrics: 0 TOS 0 Metrics: 1 Routing Bit Set on this LSA LS age: 1897 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 3.3.3.3 Advertising Router: 3.3.3.3 LS Seq Number: 80000007 Checksum: 0xCB91 Length: 48 Area Border Router Number of Links: 2 Link connected to: a Stub Network (Link ID) Network/subnet number: 3.3.3.3 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Transit Network (Link ID) Designated Router address: 172.30.0.1 (Link Data) Router Interface address: 172.30.0.3 Number of TOS metrics: 0 TOS 0 Metrics: 1 r1#
2. Network LSA – Produced by every DR in multi-access network. Network LSA floods within its own area. Describes all connected OSPF routers including the DR itself. The DR represents all connected router within its own area as a pesudonode, hence a network LSA represents a pseudonode just as a router LSA represents as a single physical router.
r1#show ip ospf database network OSPF Router with ID (1.1.1.1) (Process ID 1) Net Link States (Area 0) Routing Bit Set on this LSA LS age: 416 Options: (No TOS-capability, DC) LS Type: Network Links Link State ID: 172.30.0.1 (address of Designated Router) Advertising Router: 1.1.1.1 LS Seq Number: 80000007 Checksum: 0x92B5 Length: 36 Network Mask: /24 Attached Router: 1.1.1.1 Attached Router: 2.2.2.2 Attached Router: 3.3.3.3 r1#
3. Network Summary LSA – Produced by ABR. This LSA advertises routes outside the area, for instance R2 is the ABR of area 0 and 10. R2 advertises route to area 10 within area 0, R2 also advertises route to area 0 within area 10. Default routes external to the area, but internal to the OSPF autonomous system are also advertised by network summary LSA.
r2#show ip ospf database summary OSPF Router with ID (2.2.2.2) (Process ID 1) Summary Net Link States (Area 0) Routing Bit Set on this LSA LS age: 1846 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 4.4.4.4 (summary Network Number) Advertising Router: 3.3.3.3 LS Seq Number: 80000007 Checksum: 0x4C05 Length: 28 Network Mask: /32 TOS: 0 Metric: 201 LS age: 793 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 5.5.5.5 (summary Network Number) Advertising Router: 2.2.2.2 LS Seq Number: 80000006 Checksum: 0x3E14 Length: 28 Network Mask: /32 TOS: 0 Metric: 201 LS age: 1817 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 172.30.10.0 (summary Network Number) Advertising Router: 2.2.2.2 LS Seq Number: 80000007 Checksum: 0x7C15 Length: 28 Network Mask: /24 TOS: 0 Metric: 200 Routing Bit Set on this LSA LS age: 1850 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 172.30.20.0 (summary Network Number) Advertising Router: 3.3.3.3 LS Seq Number: 80000007 Checksum: 0xEF93 Length: 28 Network Mask: /24 TOS: 0 Metric: 200 Summary Net Link States (Area 10) LS age: 1823 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 1.1.1.1 (summary Network Number) Advertising Router: 2.2.2.2 LS Seq Number: 80000007 Checksum: 0x2702 Length: 28 Network Mask: /32 TOS: 0 Metric: 2 LS age: 1825 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 2.2.2.2 (summary Network Number) Advertising Router: 2.2.2.2 LS Seq Number: 80000007 Checksum: 0xEE37 Length: 28 Network Mask: /32 TOS: 0 Metric: 1 LS age: 1827 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 3.3.3.3 (summary Network Number) Advertising Router: 2.2.2.2 LS Seq Number: 80000007 Checksum: 0xCA56 Length: 28 Network Mask: /32 TOS: 0 Metric: 2 LS age: 1828 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 4.4.4.4 (summary Network Number) Advertising Router: 2.2.2.2 LS Seq Number: 80000007 Checksum: 0x74DF Length: 28 Network Mask: /32 TOS: 0 Metric: 202 LS age: 1829 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 172.30.0.0 (summary Network Number) Advertising Router: 2.2.2.2 LS Seq Number: 80000007 Checksum: 0x1D46 Length: 28 Network Mask: /24 TOS: 0 Metric: 1 LS age: 1831 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(Network) Link State ID: 172.30.20.0 (summary Network Number) Advertising Router: 2.2.2.2 LS Seq Number: 80000007 Checksum: 0x186E Length: 28 Network Mask: /24 TOS: 0 Metric: 201 r2#
4. ASBR summary LSA – Produced by ABR. This LSA is identical to type 3 network summary LSA except it only advertises the destination of ASBR. This LSA describes which router is doing redistribution. This LSA floods inter-area.
r2#show ip ospf database asbr-summary OSPF Router with ID (2.2.2.2) (Process ID 1) Summary ASB Link States (Area 0) LS age: 1121 Options: (No TOS-capability, DC, Upward) LS Type: Summary Links(AS Boundary Router) Link State ID: 5.5.5.5 (AS Boundary Router address) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0x3027 Length: 28 Network Mask: /0 TOS: 0 Metric: 200 r2#
As shown above, the destination of ASBR is revealed in type 4 ASBR summary LSA.
5. Autonomous System External LSA – Produced by ASBR. This LSA either advertises a destination external to OSPF autonomous system or a default route external to the OSPF autonomous system. In essence it advertises redistributed routes. This is the only LSA that is not associated with any area or area types.
r5#show ip ospf database external OSPF Router with ID (5.5.5.5) (Process ID 1) Type-5 AS External Link States LS age: 1605 Options: (No TOS-capability, DC) LS Type: AS External Link Link State ID: 192.168.0.0 (External Network Number ) Advertising Router: 5.5.5.5 LS Seq Number: 80000001 Checksum: 0xAB61 Length: 36 Network Mask: /30 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 200 Forward Address: 0.0.0.0 External Route Tag: 100 r5#
6. MOSPF – Not supported by Cisco router. If MOSPF is received by Cisco router syslog message will be generated.
r5(config)#router ospf 1 r5(config-router)#ignore lsa mospf r5(config-router)#
Ignoring mospf LSA will prevent syslog messages from being produced if mospf lsa is received.
7. NSSA LSA – Produced by ASBR of Not-so-stubby-Area type. This LSA is only flooded within NSSA, it describes redistributed routes within NSSA only. OSPF routers within NSSA must be NSSA type otherwise no adjacency can be formed.
show ip ospf database nssa-external
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