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In this guide, we’ll explore how to verify the status of your services in HashiCorp Consul using the UI, DNS interface, and HTTP API. We’ll also walk through adding a second node to the cluster and confirming that multiple service instances are correctly registered.

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Viewing Services in the Consul UI

We have a client node named web-server-01 which registers the front-end-eCommerce service. On the Consul UI home screen, you’ll see two entries:
  • consul (2 instances)
  • front-end-eCommerce (1 instance)
The image shows a web interface for HashiCorp Consul, displaying two services: "consul" with two instances and "front-end-eCommerce" with one instance.
Click front-end-eCommerce to view the service details and health check (check web on port 80), which passes since Apache is running on the host.
The image shows a web interface displaying health check statuses for a server, indicating that the agent is alive and reachable, and a successful TCP connection on port 80.

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Querying the Service Catalog

You can also query Consul programmatically via DNS or the HTTP API. Below is a quick comparison:
Query MethodCommandOutput Format
DNS (port 8600)dig @<CONSUL_IP> -p 8600 front-end-eCommerce.service.consul AA records (IP addresses)
HTTP API (port 8500)curl http://<CONSUL_IP>:8500/v1/catalog/service/front-end-eCommerce?ns=default | jqJSON array

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DNS Lookup

Consul’s built-in DNS server listens on port 8600 by default. Ensure your firewall allows UDP/TCP traffic on this port.
Run: 
dig @10.0.101.110 -p 8600 front-end-eCommerce.service.consul A
Sample output: 
;; ANSWER SECTION:
front-end-eCommerce.service.consul. 0 IN A 10.0.101.177

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HTTP API Query

Fetch the service catalog via HTTP: 
curl --request GET \
  http://54.92.155.215:8500/v1/catalog/service/front-end-eCommerce?ns=default \
  | jq
Example response: 
[
  {
    "Node": "web-server-01",
    "Address": "10.0.101.177",
    "ServiceName": "front-end-eCommerce",
    "ServiceTags": ["v7.05", "production"],
    "ServiceAddress": "10.0.101.177",
    "ServiceTaggedAddresses": {
      "lan_ipv4": { "Address": "10.0.101.177", "Port": 80 }
    }
  }
]
This output shows the node name, IP address, and metadata for each instance.

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Adding a Second Server

Let’s register web-server-02 with the same front-end-eCommerce service.
StepCommandExpected Result
Start Consul agentsudo systemctl start consulAgent is running
Join the clusterconsul join 10.0.101.110web-server-02 shows in consul members
Register the serviceconsul services register service-with-health.jsonService appears in UI

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Verifying Multiple Instances

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In the UI

Refresh the Consul UI. front-end-eCommerce now displays two healthy instances: web-server-01 and web-server-02.

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Via HTTP API

Re-run the catalog query: 
curl http://54.92.155.215:8500/v1/catalog/service/front-end-eCommerce?ns=default | jq
You’ll see both nodes: 
[
  { "Node": "web-server-01", "Address": "10.0.101.177", … },
  { "Node": "web-server-02", "Address": "10.0.101.178", … }
]

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Via DNS

Query DNS again: 
dig @10.0.101.110 -p 8600 front-end-eCommerce.service.consul A
Sample ANSWER SECTION: 
front-end-eCommerce.service.consul. 0 IN A 10.0.101.177
front-end-eCommerce.service.consul. 0 IN A 10.0.101.178
This confirms that both Consul DNS and the HTTP API correctly reflect the two running instances.

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