Task 1: Configure OSPF Area 0 with process ID 50 on all devices under their respective interfaces connected to VLAN 50. Do not use the network command under the OSPF process.

Instead of the network command, ip ospf area command can be used under each interface. For the SW50, we need to enable OSPF on its VLAN 50 interface.

On R1:

R1#configure terminal
R1(config)#interface g0/0
R1(config-if)#ip ospf 50 area 0

On R2:

R2#configure terminal
R2(config)#interface g0/0
R2(config-if)#ip ospf 50 area 0

On R3:

R3#configure terminal
R3(config)#interface g0/0
R3(config-if)#ip ospf 50 area 0

On R4:

R4#configure terminal
R4(config)#interface g0/0
R4(config-if)#ip ospf 50 area 0

On SW50:

SW50#configure terminal
SW50(config)#interface vlan50
SW50(config-if)#ip ospf 50 area 0

ip ospf 50 area 0 command allows the interfaces to participate in OSPF area 0 by sending and receiving OSPF Hello packets to form neighbor relationships and advertise the directly connected network. In this command, "50" is the process-id  which is required.

Task 2: Using a host wildcard mask, configure all the routers to advertise their respective Loopback0 networks.

A host wild card is 0.0.0.0 which is equivalent to subnet mask 255.255.255.255 (/32), which means a single address. For this task, we need to use the network command under the OSPF process.

On R1:

R1(config-if)#router ospf 50
R1(config-router)#network 1.1.1.1 0.0.0.0 area 0

On R2:

R2(config-if)#router ospf 50
R2(config-router)#network 2.2.2.2 0.0.0.0 area 0

On R3:

R3(config-if)#router ospf 50
R3(config-router)#network 3.3.3.3 0.0.0.0 area 0

On R4:

R4(config-if)#router ospf 50
R4(config-router)#network 4.4.4.4 0.0.0.0 area 0

This command advertises the exact IP address of the Loopback0 interfaces by specifying a host wildcard mask (0.0.0.0), associating it with Area 0.

Task 3: Configure R1 to always be the DR with max possible value.

On OSPF broadcast networks, the Designated Router (DR) is elected based on OSPF priority. The device with higher priority is elected as the DR. The default OSPF priority is 1 while the maximum is 255.  By setting the maximum OSPF priority (255), R1 will always win the DR election.

On R1:

R1(config-router)#interface g0/0
R1(config-if)#ip ospf priority 255.

No configuration changes are needed on the other devices because the default OSPF priority is 1. This means that they cannot compete with R1 for the DR role.

Task 4: SW50 should be configured not to participate in the DR/BDR election.

A device with 0 priority doesn't participate in DR/BDR elections.

On SW50:

SW50(config-if)#ip ospf 50 area 0

Verification:

Reset the OSPF process on the devices for configurations to take effect.

R1(config-if)end
R1#clear ip ospf process
R1#Reset ALL OSPF processes? [no]: yes

R2(config-router)end
R2#clear ip ospf process
R2#Reset ALL OSPF processes? [no]: yes

R3(config-router)end
R3#clear ip ospf process
R3#Reset ALL OSPF processes? [no]: yes

R4(config-router)end
R4#clear ip ospf process
R4#Reset ALL OSPF processes? [no]: yes

SW50(config-if)end
SW50#clear ip ospf process
SW50#Reset ALL OSPF processes? [no]: yes

Now check if R1 is the DR by using show ip ospf neighbor command on any of the devices.

R2#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface

1.1.1.1         255   FULL/DR         00:00:32    10.0.0.1        GigabitEthernet0/0

10.0.0.5          0   2WAY/DROTHER    00:00:37    10.0.0.5        GigabitEthernet0/0

4.4.4.4           1   FULL/BDR        00:00:36    10.0.0.4        GigabitEthernet0/0

3.3.3.3           1   2WAY/DROTHER    00:00:32    10.0.0.3        GigabitEthernet0/0

Full/DR means that R1 is the DR. SW50 has priority of 0 so it is neither DR nor BDR and doesn't participate in the election. Routers in the network form full adjacencies (reach the FULL state) only with the DR and BDR. Non-DR/BDR routers form a 2WAY state with each other to conserve resources and avoid redundant link-state updates. That is why R2 is in a 2WAY state with the other DROTHERs

Now save the configuration.

R1#write memory

R2#write memory

R3#write memory

R4#write memory

SW50#write memory