Basic configuration:
R1:
ipv uni
!
interface Serial1/0
ip address 12.0.0.1 255.255.255.0
ip ospf 1 area 0
ipv6 address 12::1/64
ipv6 ospf 1 area 0
!
router ospf 1
router-id 0.0.0.1
!
ipv6 router ospf 1
router-id 0.0.0.1
R2:
ipv uni
!
interface Serial1/0
ip address 12.0.0.2 255.255.255.0
ip ospf 1 area 0
ipv6 address 12::2/64
ipv6 ospf 1 area 0
no sh
!
interface Serial1/1
ip address 23.0.0.2 255.255.255.0
ip ospf 1 area 0
ipv6 address 23::2/64
ipv6 ospf 1 area 0
no sh
!
router ospf 1
router-id 0.0.0.2
!
ipv6 router ospf 1
router-id 0.0.0.2
R3:
ipv uni
!
interface Serial1/0
ip address 23.0.0.3 255.255.255.0
ip ospf 1 area 0
ipv6 address 23::3/64
ipv6 ospf 1 area 0
no sh
!
router ospf 1
router-id 0.0.0.3
!
ipv6 router ospf 1
router-id 0.0.0.3
In OSPFv2 the sh ip ospf neighbor command has some informations that indicate:
The Neighbor ID is the router ID of the neighbor router.
The Pri field indicates the priority of the neighbor router.
The State field indicates the functional state of the neighbor router.
The Dead Time field indicates the amount of time remaining that the router waits to receive an OSPF hello packet from the neighbor before declaring the neighbor down
The Address field indicates the IP address of the interface to which this neighbor is directly connected. This is the IP address of the neighbor.
The Interface field indicates the interface on which the OSPF neighbor has formed adjacency.
R1#sh ip os nei
Neighbor ID Pri State Dead Time Address Interface
0.0.0.2 0 FULL/ - 00:00:31 12.0.0.2 Serial1/0
R1#
R2#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
0.0.0.3 0 FULL/ - 00:00:33 23.0.0.3 Serial1/1
0.0.0.1 0 FULL/ - 00:00:32 12.0.0.1 Serial1/0
R2#
R2#sh ip os nei
Neighbor ID Pri State Dead Time Address Interface
0.0.0.1 0 FULL/ - 00:00:37 12.0.0.1 Serial1/0
R2#
In OSPFv2, the Type-1 LSA describes the Links connected to the router, there are four Links Type.
Link Type 1: Point-to-point connection to another router = Neighbor router ID
Link Type 2: Connection to a transit network = DR's interface address
Link Type 3: Connection to a stub network = IP network/subnet number
Link Type 4: Virtual Link = Neighbor router ID
The Link Type 1 describes who is connected to me, let's display the Type-1 LSA ' s R1:
The line "Link connected to: another Router (point-to-point)" represents the Link Type 1.
"(Link ID) Neighboring Router ID: 0.0.0.2" represents the router ID of R2.
"(Link Data) Router Interface address: 12.0.0.1" represents the IP address of R1 connected to R2.
R1# sh ip os data router self
OSPF Router with ID (0.0.0.1) (Process ID 1)
Router Link States (Area 0)
LS age: 1158
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 0.0.0.1
Advertising Router: 0.0.0.1
LS Seq Number: 80000002
Checksum: 0xBFC6
Length: 48
Number of Links: 2
Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID: 0.0.0.2
(Link Data) Router Interface address: 12.0.0.1
Number of MTID metrics: 0
TOS 0 Metrics: 64
Link connected to: a Stub Network
(Link ID) Network/subnet number: 12.0.0.0
(Link Data) Network Mask: 255.255.255.0
Number of MTID metrics: 0
TOS 0 Metrics: 64
R1#
Let's verify the Type-LSA ' s R2:
"(Link Data) Router Interface address: 12.0.0.2" represents the IP address of R2 connected to R1.
R1#sh ip os data router adv 0.0.0.2
OSPF Router with ID (0.0.0.1) (Process ID 1)
Router Link States (Area 0)
LS age: 645
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 0.0.0.2
Advertising Router: 0.0.0.2
LS Seq Number: 80000003
Checksum: 0x4071
Length: 72
Number of Links: 4
Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID: 0.0.0.3
(Link Data) Router Interface address: 23.0.0.2
Number of MTID metrics: 0
TOS 0 Metrics: 64
Link connected to: a Stub Network
(Link ID) Network/subnet number: 23.0.0.0
(Link Data) Network Mask: 255.255.255.0
Number of MTID metrics: 0
TOS 0 Metrics: 64
Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID: 0.0.0.1
(Link Data) Router Interface address: 12.0.0.2
Number of MTID metrics: 0
TOS 0 Metrics: 64
Link connected to: a Stub Network
(Link ID) Network/subnet number: 12.0.0.0
(Link Data) Network Mask: 255.255.255.0
Number of MTID metrics: 0
TOS 0 Metrics: 64
R1#
Since the Type-1 LSA describes through the Link Type 1 the router ID of the neighbor and the IP address connected to this neighbor.
The Adjacency table displays the router ID in the neighbor ID field and the IP address of this neighbor in the Address field as shown by the show ip os nei on R1 and R2:
R1#sh ip os nei
Neighbor ID Pri State Dead Time Address Interface
0.0.0.2 0 FULL/ - 00:00:31 12.0.0.2 Serial1/0
R1#
R2#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
0.0.0.3 0 FULL/ - 00:00:33 23.0.0.3 Serial1/1
0.0.0.1 0 FULL/ - 00:00:32 12.0.0.1 Serial1/0
R2#
What about OSPFv3?
Let's verify the adjacency tables of R1 and R2:
R2#sh ipv os nei
OSPFv3 Router with ID (0.0.0.2) (Process ID 1)
Neighbor ID Pri State Dead Time Interface ID Interface
0.0.0.3 0 FULL/ - 00:00:31 4 Serial1/1
0.0.0.1 0 FULL/ - 00:00:33 4 Serial1/0
R2#
The only difference is that the Address field is replaced by the Interface ID, this the Interface ID of the neighbor R2 = 4.
R1#sh ipv os nei
OSPFv3 Router with ID (0.0.0.1) (Process ID 1)
Neighbor ID Pri State Dead Time Interface ID Interface
0.0.0.2 0 FULL/ - 00:00:38 4 Serial1/0
R1#
Per RFC 5340 OSPF for IPv6
2.7. Packet Format Changes
The Hello packet now contains no address information at all.
Rather, it now includes an Interface ID that the originating
router has assigned to uniquely identify (among its own
interfaces) its interface to the link. This Interface ID will be
used as the network-LSA's Link State ID if the router becomes the
Designated Router on the link.
4.1.2. The Interface Data Structure
In OSPF for IPv6, an interface connects a router to a link. The IPv6
interface structure modifies the IPv4 interface structure (as defined
in Section 9 of [OSPFV2]) as follows:
Interface ID
Every interface is assigned an Interface ID, which uniquely
identifies the interface with the router. For example, some
implementations MAY be able to use the MIB-II IfIndex ([INTFMIB])
as the Interface ID. The Interface ID appears in Hello packets
sent out the interface, the link-local-LSA originated by the
router for the attached link, and the router-LSA originated by the
router-LSA for the associated area. It will also serve as the
Link State ID for the network-LSA that the router will originate
for the link if the router is elected Designated Router.
The Interface ID for a virtual link is independent of the
Interface ID of the outgoing interface it traverses in the transit
area.7
How R1 get the Interface ID of R2?
Let's verify the Type-LSA 1 's R2:
The Type-1 LSA of R2 carries two links, they describe the neighbors connected to R2.
The first link identifies the neighbor ID 0.0.0.3 which is R3.
The second link identifies the neighbor ID 0.0.0.1 which is R1.
"Router Interface address" field is no longer present, instead R2 adds two field:
The Local Interface ID: 4
The Neighbor Interface ID: 4
R1#sh ipv os data router adv 0.0.0.2
OSPFv3 Router with ID (0.0.0.1) (Process ID 1)
Router Link States (Area 0)
LS age: 1175
Options: (V6-Bit, E-Bit, R-bit, DC-Bit)
LS Type: Router Links
Link State ID: 0
Advertising Router: 0.0.0.2
LS Seq Number: 80000002
Checksum: 0x4017
Length: 56
Number of Links: 2
Link connected to: another Router (point-to-point)
Link Metric: 64
Local Interface ID: 5
Neighbor Interface ID: 4
Neighbor Router ID: 0.0.0.3
Link connected to: another Router (point-to-point)
Link Metric: 64
Local Interface ID: 4
Neighbor Interface ID: 4
Neighbor Router ID: 0.0.0.1
R1#
Where R2 get the Local Interface ID and the Neighbor Interface ID ?
In OSPFv3: The LSA Type 8 is used to advertise the link-local address of the router's interface to the routers attached to the link in order to use these link-local addresses for the next-hop,also it informs the routers attached to the link the list of prefixes associated with the link.
The Link State ID is set to the router's Interface ID on Link.
Let's see the Type-LSA 8 of R2:, we can see that the Link State ID of the Link LSA 's R2 is 4 (Interface ID).
When R2 builds its own Type-LSA 1 it puts the Local Interface ID to 4 (own Interface ID).
R1#sh ipv os data link adv 0.0.0.2
OSPFv3 Router with ID (0.0.0.1) (Process ID 1)
Link (Type-8) Link States (Area 0)
LS age: 729
Options: (V6-Bit, E-Bit, R-bit, DC-Bit)
LS Type: Link-LSA (Interface: Serial1/0)
Link State ID: 4 (Interface ID)
Advertising Router: 0.0.0.2
LS Seq Number: 80000002
Checksum: 0x8308
Length: 56
Router Priority: 1
Link Local Address: FE80::C802:6FF:FECC:8
Number of Prefixes: 1
Prefix Address: 12::
Prefix Length: 64, Options: None
R1#
The same process is followed by R1, it creates a Type-8 LSA with the Link State ID: 4 (own Interface ID) and puts it as the Local Interface ID in its Type-1 LSA:
R1#sh ipv os data link self
OSPFv3 Router with ID (0.0.0.1) (Process ID 1)
Link (Type-8) Link States (Area 0)
LS age: 959
Options: (V6-Bit, E-Bit, R-bit, DC-Bit)
LS Type: Link-LSA (Interface: Serial1/0)
Link State ID: 4 (Interface ID)
Advertising Router: 0.0.0.1
LS Seq Number: 80000003
Checksum: 0x5C24
Length: 56
Router Priority: 1
Link Local Address: FE80::C801:AFF:FED4:8
Number of Prefixes: 1
Prefix Address: 12::
Prefix Length: 64, Options: None
R1#
R1#sh ipv os data router self
OSPFv3 Router with ID (0.0.0.1) (Process ID 1)
Router Link States (Area 0)
LS age: 1072
Options: (V6-Bit, E-Bit, R-bit, DC-Bit)
LS Type: Router Links
Link State ID: 0
Advertising Router: 0.0.0.1
LS Seq Number: 80000003
Checksum: 0x3B78
Length: 40
Number of Links: 1
Link connected to: another Router (point-to-point)
Link Metric: 64
Local Interface ID: 4
Neighbor Interface ID: 4
Neighbor Router ID: 0.0.0.2
R1#
Finally the Interface ID in the Adjacency table of R1 represents the Interface ID = 4 of the neighbor R2, which is the Link State ID of the Type-8 LSA 's R2:
R1#sh ipv os nei
OSPFv3 Router with ID (0.0.0.1) (Process ID 1)
Neighbor ID Pri State Dead Time Interface ID Interface
0.0.0.2 0 FULL/ - 00:00:38 4 Serial1/0
R1#
Let's verify the neighbor table of R3, R3 is adjacent with R2, the Interface ID is 5, this is the Link State ID of the Type-8 LSA's R2:
R3#sh ipv os nei
OSPFv3 Router with ID (0.0.0.3) (Process ID 1)
Neighbor ID Pri State Dead Time Interface ID Interface
0.0.0.2 0 FULL/ - 00:00:38 5 Serial1/0
R3#
Let's verify the Type-8 LSA 's R2 using the sh ipv os data link adv 0.0.0.2 command, the Link State ID is = 5 (Interface ID):
Note: in OSPFv3, each router creates a single Type-8 LSA for each Link, each Type-8 LSA has a unique Link State ID.
The Type-8 LSA 's R2 in Link R1--R2 has a Link State ID: 4.
The Type-8 LSA 's R2 in Link R2--R3 has a Link State ID: 5.
R3#sh ipv os data link adv 0.0.0.2
OSPFv3 Router with ID (0.0.0.3) (Process ID 1)
Link (Type-8) Link States (Area 0)
LS age: 499
Options: (V6-Bit, E-Bit, R-bit, DC-Bit)
LS Type: Link-LSA (Interface: Serial1/0)
Link State ID: 5 (Interface ID)
Advertising Router: 0.0.0.2
LS Seq Number: 80000003
Checksum: 0x99DE
Length: 56
Router Priority: 1
Link Local Address: FE80::C802:6FF:FECC:8
Number of Prefixes: 1
Prefix Address: 23::
Prefix Length: 64, Options: None
R3#
The Type-1 LSA 's R2 lists the Local Interface ID: 5 (the Link State ID ot its Type-8 LSA) in the Link Type 1 that describes the connection to another router, R3 in this case:
R3#sh ipv os data router adv 0.0.0.2
OSPFv3 Router with ID (0.0.0.3) (Process ID 1)
Router Link States (Area 0)
LS age: 478
Options: (V6-Bit, E-Bit, R-bit, DC-Bit)
LS Type: Router Links
Link State ID: 0
Advertising Router: 0.0.0.2
LS Seq Number: 80000003
Checksum: 0x3E18
Length: 56
Number of Links: 2
Link connected to: another Router (point-to-point)
Link Metric: 64
Local Interface ID: 5
Neighbor Interface ID: 4
Neighbor Router ID: 0.0.0.3
Link connected to: another Router (point-to-point)
Link Metric: 64
Local Interface ID: 4
Neighbor Interface ID: 4
Neighbor Router ID: 0.0.0.1
R3#
R3 creates a Type-1 LSA and sets the Neighbor Interface ID: 5, this is the Link State ID of the Type-8 LSA 's R2 and sees R2 as the neighbor:
R3#sh ipv os data router self
OSPFv3 Router with ID (0.0.0.3) (Process ID 1)
Router Link States (Area 0)
LS age: 326
Options: (V6-Bit, E-Bit, R-bit, DC-Bit)
LS Type: Router Links
Link State ID: 0
Advertising Router: 0.0.0.3
LS Seq Number: 80000003
Checksum: 0x416F
Length: 40
Number of Links: 1
Link connected to: another Router (point-to-point)
Link Metric: 64
Local Interface ID: 4
Neighbor Interface ID: 5
Neighbor Router ID: 0.0.0.2
R3#
Finally R3 creates one Type-8 LSA with a Link State ID: 4, this the Interface ID that R2 displays in the Adjacency table:
R3#sh ipv os data link self
OSPFv3 Router with ID (0.0.0.3) (Process ID 1)
Link (Type-8) Link States (Area 0)
LS age: 383
Options: (V6-Bit, E-Bit, R-bit, DC-Bit)
LS Type: Link-LSA (Interface: Serial1/0)
Link State ID: 4 (Interface ID)
Advertising Router: 0.0.0.3
LS Seq Number: 80000003
Checksum: 0x93F0
Length: 56
Router Priority: 1
Link Local Address: FE80::C803:DFF:FEB8:8
Number of Prefixes: 1
Prefix Address: 23::
Prefix Length: 64, Options: None
R3#
The Adjacency table of R2 shown:
1-The Interface ID: 4 (the Link State ID of the Type-8 LSA 's R3) for the entry 0.0.0.3.
1-The Interface ID: 4 (the Link State ID of the Type-8 LSA 's R2) for the entry 0.0.0.1.
R2#sh ipv os nei
OSPFv3 Router with ID (0.0.0.2) (Process ID 1)
Neighbor ID Pri State Dead Time Interface ID Interface
0.0.0.3 0 FULL/ - 00:00:31 4 Serial1/1
0.0.0.1 0 FULL/ - 00:00:33 4 Serial1/0
R2#
Finally:
1-In OSPFv2: The "Address" field indicates the IP address of the interface to which this neighbor is directly connected. This is the IP address of the neighbor.
2-In OSPFv3: There is no "Address" field, instead OSPFv3 replaces it with the "Interface ID", it indicates the "Link State ID" of the Type-8 LSA advertised by the neighbor. In other words the "Local Interface ID" of the Type-1 LSA originated by the neighbor.