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In this section, we reviewed the essential steps to install, configure, and operate Consul agents in both server and client modes.

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Key Takeaways

TaskDescriptionExample/Command
Agent StartupLaunch Consul from the CLI or via a JSON/HCL config fileconsul agent -dev -bind 192.168.1.10
Configuration FormatsDefine common settings, server/client roles, and register servicesHCL or JSON snippets
Network Binding & PortsSet bind_addr, and customize RPC, HTTP, and DNS port assignmentsbind_addr = "0.0.0.0"
Cluster Join & LeaveAdd nodes with consul join and gracefully remove them using consul leaveconsul join 10.0.0.1
Before restarting agents, validate your configuration:
consul validate /path/to/config.hcl

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1. Starting and Managing the Consul Process

You can start a Consul agent directly from the command line: 
consul agent \
  -dev \
  -bind 192.168.1.10 \
  -config-dir /etc/consul.d
Or use an HCL/JSON configuration file (consul.hcl): 
datacenter       = "dc1"
node_name        = "consul-server-1"
server           = true
bootstrap_expect = 3
bind_addr        = "0.0.0.0"

ports {
  http = 8500
  rpc  = 8400
  dns  = 8600
}

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2. Interpreting Consul Agent Configurations

Both HCL and JSON support the same agent options.
Example HCL for a client agent registering a web service: 
service {
  name = "web"
  port = 80
  tags = ["nginx", "frontend"]
}

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3. Configuring Network Addresses and Ports

Fine-tune Consul network settings to optimize performance and security:
  • bind_addr: IP/interface for RPC, HTTP, DNS
  • advertise_addr: Publicly advertised address
  • ports.rpc, ports.http, ports.dns
bind_addr = "10.0.0.5"
advertise_addr = "203.0.113.10"

ports {
  http = 8500
  rpc  = 8400
  dns  = 8600
}

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4. Agent Join and Leave Behaviors

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Joining a Cluster

Use the consul join command to add a new node: 
consul join 10.0.0.1 10.0.0.2

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Graceful Leave

For clients and especially servers, remove nodes gracefully to maintain cluster health: 
consul leave
Always drain and remove server nodes gracefully to avoid quorum loss.
Use consul leave rather than killing the process.

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Next Steps

Move on to Objective 3: Service Discovery & Health Checking to learn how Consul automatically tracks and verifies service health.

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