Redundant server configuration in SCADA systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of Redundant Server Configuration

Why is redundant server configuration important in SCADA systems?

A To simplify the network by removing backup servers

B To ensure continuous operation by switching to backup servers if the main server fails

C To reduce the number of servers needed by consolidating tasks on one server

D To increase the speed of data processing by using multiple servers simultaneously

💡 Hint

Think about what happens if the main server stops working unexpectedly.

Redundant server configuration provides backup servers that take over automatically if the main server fails, ensuring the SCADA system keeps running without interruption.

💻 Command Output

intermediate

Check Active Server in Redundant Setup

What is the output of the command show redundancy status when the primary server is active?

SCADA systems

show redundancy status

A Primary server: Failed\nBackup server: Active

B Primary server: Standby\nBackup server: Active

C Primary server: Active\nBackup server: Standby

D No redundancy configured

💡 Hint

Consider which server is active when the system is working normally.

The primary server is active and handling operations, while the backup server is on standby waiting to take over if needed.

❓ Configuration

advanced

Configuring Heartbeat Between Redundant Servers

Which configuration snippet correctly sets up a heartbeat link between two redundant SCADA servers?

A heartbeat interface eth2\nheartbeat interval 5

B heartbeat interface eth0\nheartbeat interval 10\nheartbeat timeout 2

C heartbeat interface eth1\nheartbeat interval 0\nheartbeat timeout 10

D heartbeat interface eth1\nheartbeat interval 2\nheartbeat timeout 6

💡 Hint

Heartbeat interval should be less than timeout and interface must be valid.

Option D correctly configures the heartbeat on interface eth1 with a 2-second interval and 6-second timeout, ensuring timely detection of failures.

❓ Troubleshoot

advanced

Troubleshooting Failover Failure

After configuring redundant servers, failover does not occur when the primary server fails. What is the most likely cause?

A Heartbeat link between servers is down or misconfigured

B Backup server has higher priority than primary

C Primary server is set to standby mode

D Network cables are connected properly

💡 Hint

Failover depends on servers communicating their status regularly.

If the heartbeat link is down or misconfigured, servers cannot detect failure and failover will not trigger.

🔀 Workflow

expert

Order of Steps to Add a Backup Server

What is the correct order to add a new backup server to an existing SCADA redundant server setup?

A 1,2,3,4

B 1,3,2,4

C 2,1,3,4

D 3,1,2,4

💡 Hint

Think about preparing the backup server first, then syncing, then monitoring, then testing.

The backup server must first have network configured, then receive the primary's config, then heartbeat enabled, and finally tested for failover.