Consul 1.15 Practice Exam 4 — 20 Questions

Question 1

What happens to the gossip protocol if the 'encrypt' key is mismatched between two datacenters trying to join via WAN?

Accepted Answer

The join fails.. If the encryption keys do not match, the agents will be unable to decrypt the gossip packets and the join will fail.

Answer

The join proceeds with warnings.

Answer

The connection defaults to unencrypted.

Answer

Only metadata is encrypted.

Question 2

How do you enable WAN federation between two Consul datacenters that do not share a network?

Accepted Answer

By deploying Mesh Gateways.. Mesh gateways allow cross-datacenter communication in environments where direct WAN gossip is not possible.

Answer

By disabling ACLs.

Answer

By increasing the gossip interval.

Answer

By using a load balancer in front of the servers.

Question 3

Which THREE items are required when configuring ACL replication in Consul?

Accepted Answer

The 'acl_replication' configuration block enabled.. ACL replication needs a defined primary, a valid token for reading, and the enabled replication flag.

Answer

A global root ACL token on every client node.

Answer

The 'raft_protocol' version set to 1.

Question 4

When a service check transitions to 'critical', what does Consul do with the service's DNS entry?

Accepted Answer

It removes the instance from the DNS response.. Consul removes the service instance from DNS results when its health check is critical.

Answer

It marks the record as 'stale'.

Answer

It returns the IP but with a low TTL.

Answer

It returns a 503 status code.

Question 5

What is the role of a Consul server in a non-primary datacenter regarding ACLs?

Accepted Answer

They replicate the ACL state from the primary.. Secondary servers in an ACL-replicated setup act as a read-only mirror of the primary's ACL policy set.

Answer

They ignore all ACLs.

Answer

They can write new ACL policies independently.

Answer

They become the primary if the original primary fails.

Question 6

To verify if two datacenters are connected via WAN, which command shows the remote datacenter's server nodes?

Accepted Answer

consul members -wan. The 'consul members -wan' command lists all nodes participating in the WAN gossip pool, regardless of their local datacenter.

Answer

consul members

Answer

consul info

Answer

consul operator raft list-peers

Question 7

Which THREE factors influence cross-datacenter service discovery resolution?

Accepted Answer

The local server must have knowledge of the remote datacenter's server addresses.. Resolution depends on the ability to query the remote DC, the health status of the remote instances, and the configuration of the local discovery agent.

Answer

All services must be in the same namespace.

Answer

The local agent must have superuser permissions.

Question 8

You are joining two Consul datacenters via WAN gossip. Which command must be executed on a Consul server in the secondary datacenter to initiate the federation?

Accepted Answer

consul join -wan <remote-server-address>. The consul join command with the -wan flag is the standard mechanism to introduce a node from one datacenter into the WAN gossip pool of another.

Answer

consul members -wan

Answer

consul reload -wan

Answer

consul agent -join-wan

Question 9

Which TWO of the following describe a Consul 'service definition'?

Accepted Answer

A configuration that the agent watches for changes.. They are JSON/HCL files and are monitored by the agent.

Answer

A database-specific configuration.

Answer

A static, immutable file.

Answer

A binary file loaded into the server.

Question 10

A service in datacenter A needs to call a service in datacenter B. If 'prepared_queries' are not used, how does the service discovery query look?

Accepted Answer

.service..consul. When not using prepared queries, standard DNS discovery across DCs follows the pattern .service..consul.

Answer

<service>.service.consul

Answer

..service.consul

Answer

remote.<service>.service.consul

Question 11

You have a service that needs to talk to a service in a different datacenter. What configuration is required?

Accepted Answer

A mesh gateway deployment.. Mesh gateways are required to route cross-datacenter traffic in a Consul Connect mesh.

Answer

Direct VPC peering.

Answer

An external service definition.

Answer

A global intention.

Question 12

Which file path is standard for storing the Consul server configuration, including WAN settings?

Accepted Answer

/etc/consul.d. The '/etc/consul.d' directory is the standard location for Consul configuration files on Linux systems.

Answer

/tmp/consul

Answer

/opt/consul/bin

Answer

/var/lib/consul

Question 13

Which THREE configuration items are part of a complete WAN gossip setup?

Accepted Answer

The 'server' role flag set to true.. WAN setup requires joining the WAN pool, defining the server role, and potentially setting encryption.

Answer

The 'client_addr' restricted to local only.

Answer

The 'ui' configuration set to true.

Question 14

When using multiple datacenters, what is the primary role of the 'consul-template' tool?

Accepted Answer

To generate configuration files based on Consul data.. Consul-template is often used to watch for changes in the Consul catalog and update application configurations, which can be useful when reflecting cross-DC service information.

Answer

To provision infrastructure.

Answer

To replicate KV stores.

Answer

To manage the Consul cluster nodes.

Question 15

Which TWO of the following are true about Consul datacenters?

Accepted Answer

Each datacenter must have at least one server node.. Datacenters are logical groupings and require independent server quorums.

Answer

They are strictly physical locations.

Answer

They must share the same Raft quorum.

Answer

They allow a single Consul agent to join multiple DCs.

Question 16

When configuring an ACL policy for cross-datacenter access, what policy rule is necessary to read service information from a remote datacenter?

Accepted Answer

node_prefix "" { policy = "read" }. You need 'service_prefix' or 'node_prefix' policies that explicitly allow reading in the target datacenter.

Answer

service_prefix "*" { policy = "write" }

Answer

agent_prefix "" { policy = "read" }

Answer

acl_prefix "" { policy = "read" }

Question 17

What is the primary role of the Consul Connect 'upstream' configuration?

Accepted Answer

To define the services that a local service can connect to.. Upstreams define the dependencies of a service, allowing the proxy to route to specific services.

Answer

To set intention priority.

Answer

To register external services.

Answer

To define health check ports.

Question 18

Which THREE of the following fields are typically included in a service metadata (meta) block?

Accepted Answer

environment. Meta is used for arbitrary key-value pairs to support application logic.

Answer

kernel_version

Answer

password

Question 19

What is the recommended number of Consul servers per datacenter to ensure high availability?

Accepted Answer

3. The recommended number for a consensus-based system like Consul is 3 or 5, to tolerate n/2-1 failures.

Answer

2

Answer

1

Answer

10

Question 20

You have a service that requires specific routing logic based on the environment. How can you distinguish between 'production' and 'staging' instances of the same service name using metadata?

Accepted Answer

Apply 'production' or 'staging' tags to the service definition.. Service tags are the standard way to categorize and filter services within the Consul catalog.

Answer

Use different service names for every environment.

Answer

Modify the service's port number.

Answer

Assign different Consul datacenters.