3

When I show the ospf database:

Router2#show ip ospf database 
            OSPF Router with ID (2.2.2.2) (Process ID 1)

                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
2.2.2.2         2.2.2.2         167         0x80000006 0x008e13 3
3.3.3.3         3.3.3.3         167         0x80000003 0x007660 2
1.1.1.1         1.1.1.1         99          0x80000005 0x004db8 2

                Net Link States (Area 0)
Link ID         ADV Router      Age         Seq#       Checksum
10.0.23.2       2.2.2.2         167         0x80000001 0x00dfc5
10.0.12.1       1.1.1.1         99          0x80000003 0x0014aa

I want to know

  1. the definition of Router Link and Net Link.
  2. the ADV of ADV Router.
  3. how to show the DR/BDR?

1 Answer 1

5

Router Link States are type 1 LSAs. It lists all the routers in the area and the number of interfaces. 2.2.2.2 has 3 interfaces.

Net Link States are the multi-access networks (Type 2 LSAs). The ADV (advertising router) is the DR.

You can see (or infer) the DR and BDR with the command

show ip ospf neighbors

The loopback interface is a virtual interface on the router. Since it is not dependent on the hardware, it will always be in the UP state. Cisco routers will use the highest loopback IP address as the router ID, unless you set the ID manually.

2
  • Thanks for your answer, may I ask you a more question? You see in the Router Link States the ADV Router 2.2.2.2 have 3 Link count, one is link to the loopback0(2.2.2.2), how about the other 2? is it link to its own interfaces? or the other routers' interfaces?
    – 26334_zeal
    Nov 23, 2018 at 2:32
  • It's the number of interfaces in the OSPF domain on that router. So that means all the interfaces that have OSPF enabled, including loopbacks.
    – Ron Trunk
    Nov 23, 2018 at 13:15

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