Can you confirm that link state databases are identical? Compare the output of the command show ip ospf databases from the Cisco routers and the Linux PCs.

What will be an ideal response?

The following data shows that link state information is same. Net link states indicate the global network topology of the OSPF routing environment. A router’s usable interfaces and reachable neighbors are reflected in the Link State Database (LSD). Each router sees itself as the root of the LSD. Similar to the fields of a LSA, the first column is the link state ID, the second column is the advertising router, the third column is the LS age (seconds since the last LSA was originated), and the fourth column is the LS checksum. A link state advertisement is
identified by its LS type, LS ID, and advertising router. For two instances of the same advertisement, the LS sequence number, LS age, and LS checksum fields are used to determine which is more recent. Because all routers and PCs are in the same area, the database contains two parts. One is router link states and another is net link states. The Designated Router originates the network- LSA on the subnet’s behalf. OSPF uses the network-LSA to indicate the state of database synchronization. The link state IP of the network-LSA is the IP address of the designated router; when a router-LSA includes a link to the network-LSA, the originating router is saying, “I have an interface on this subnet and my database is synchronized with the Designated Router.” Likewise the network-LSA lists those routers whose databases have been synchronized eth the Designated Router.
? PC1 :
```
ospfd# show ip ospf database
OSPF Router with ID (10.0.1.1)
Router Link States (Area 0.0.0.1)
Link ID ADV Router Age Seq# CkSum Link count
10.0.1.1 10.0.1.1 1644 0x80000029 0x1a9f 2
10.0.3.3 10.0.3.3 1235 0x80000008 0xd2d5 2
10.0.3.4 10.0.3.4 1651 0x80000015 0xecc7 2
10.0.4.5 10.0.4.5 1391 0x80000005 0x257a 2
10.0.5.2 10.0.5.2 503 0x8000001a 0x5069 2
10.0.6.6 10.0.6.6 1703 0x80000017 0x6318 2
10.0.6.7 10.0.6.7 467 0x8000001c 0x1e6b 2
10.0.7.8 10.0.7.8 534 0x8000001a 0x8627 1
Link ID ADV Router Age Seq# CkSum
10.0.1.2 10.0.5.2 1791 0x80000008 0x6daa
10.0.2.5 10.0.4.5 1391 0x80000004 0x5887
10.0.3.4 10.0.3.4 1646 0x80000005 0x739f
10.0.4.4 10.0.3.4 1753 0x80000005 0x8d81
10.0.5.2 10.0.5.2 503 0x80000006 0xb853
10.0.6.7 10.0.6.7 542 0x80000005 0x9763
10.0.7.7 10.0.6.7 466 0x80000006 0xaf46
```
? PC2 :
```
ospfd# show ip ospf database
OSPF Router with ID (10.0.5.2)
Router Link States (Area 0.0.0.1)
Link ID ADV Router Age Seq# CkSum Link count
10.0.1.1 10.0.1.1 1763 0x80000029 0x1a9f 2
10.0.3.3 10.0.3.3 1355 0x80000008 0xd2d5 2
10.0.3.4 10.0.3.4 1770 0x80000015 0xecc7 2
10.0.4.5 10.0.4.5 1511 0x80000005 0x257a 2
10.0.5.2 10.0.5.2 621 0x8000001a 0x5069 2
10.0.6.6 10.0.6.6 3 0x80000018 0x6119 2
10.0.6.7 10.0.6.7 584 0x8000001c 0x1e6b 2
10.0.7.8 10.0.7.8 652 0x8000001a 0x8627 1
Link ID ADV Router Age Seq# CkSum
10.0.1.2 10.0.5.2 108 0x80000009 0x6bab
10.0.2.5 10.0.4.5 1511 0x80000004 0x5887
10.0.3.4 10.0.3.4 1765 0x80000005 0x739f
10.0.4.4 10.0.3.4 72 0x80000006 0x8b82
10.0.5.2 10.0.5.2 621 0x80000006 0xb853
10.0.6.7 10.0.6.7 660 0x80000005 0x9763
10.0.7.7 10.0.6.7 583 0x80000006 0xaf46
```
? PC3 :
```
ospfd# show ip ospf database
OSPF Router with ID (10.0.3.4)
Router Link States (Area 0.0.0.1)
Link ID ADV Router Age Seq# CkSum Link count
10.0.1.1 10.0.1.1 8 0x8000002a 0x18a0 2
10.0.3.3 10.0.3.3 1397 0x80000008 0xd2d5 2
10.0.3.4 10.0.3.4 11 0x80000016 0xeac8 2
10.0.4.5 10.0.4.5 1553 0x80000005 0x257a 2
10.0.5.2 10.0.5.2 667 0x8000001a 0x5069 2
10.0.6.6 10.0.6.6 49 0x80000018 0x6119 2
10.0.6.7 10.0.6.7 631 0x8000001c 0x1e6b 2
10.0.7.8 10.0.7.8 698 0x8000001a 0x8627 1
Net Link States (Area 0.0.0.1)
Link ID ADV Router Age Seq# CkSum
10.0.1.2 10.0.5.2 155 0x80000009 0x6bab
10.0.2.5 10.0.4.5 1553 0x80000004 0x5887
10.0.3.4 10.0.3.4 6 0x80000006 0x71a0
10.0.4.4 10.0.3.4 113 0x80000006 0x8b82
10.0.5.2 10.0.5.2 667 0x80000006 0xb853
10.0.6.7 10.0.6.7 706 0x80000005 0x9763
10.0.7.7 10.0.6.7 630 0x80000006 0xaf46
```
? PC4 :
```
ospfd# show ip ospf database
OSPF Router with ID (10.0.6.7)
Router Link States (Area 0.0.0.1)
Link ID ADV Router Age Seq# CkSum Link count
10.0.1.1 10.0.1.1 57 0x8000002a 0x18a0 2
10.0.3.3 10.0.3.3 1449 0x80000008 0xd2d5 2
10.0.3.4 10.0.3.4 64 0x80000016 0xeac8 2
10.0.4.5 10.0.4.5 1604 0x80000005 0x257a 2
10.0.5.2 10.0.5.2 714 0x8000001a 0x5069 2
10.0.6.6 10.0.6.6 94 0x80000018 0x6119 2
10.0.6.7 10.0.6.7 674 0x8000001c 0x1e6b 2
10.0.7.8 10.0.7.8 742 0x8000001a 0x8627 1
Net Link States (Area 0.0.0.1)
Link ID ADV Router Age Seq# CkSum
10.0.1.2 10.0.5.2 202 0x80000009 0x6bab
10.0.2.5 10.0.4.5 1604 0x80000004 0x5887
10.0.3.4 10.0.3.4 59 0x80000006 0x71a0
10.0.4.4 10.0.3.4 166 0x80000006 0x8b82
10.0.5.2 10.0.5.2 714 0x80000006 0xb853
10.0.6.7 10.0.6.7 749 0x80000005 0x9763
10.0.7.7 10.0.6.7 673 0x80000006 0xaf46
```