## Understanding Loops in Ansible Loops in Ansible are used to repeat tasks multiple times. Ansible provides several keywords for looping, including `loop`, `with_`, and `until`. These enable you to execute a task iteratively with different parameters, simplifying repetitive configurations. ### Example: Configuring NTP Servers on a Router Let's consider an Ansible playbook that configures NTP (Network Time Protocol) on a router: ```yaml --- - name: "Configure NTP" hosts: router gather_facts: false tasks: - name: "Configure NTP on Router" vars: ntp_server: - "1.1.1.1" - "2.2.2.2" - "3.3.3.3" - "4.4.4.4" cisco.ios.ios_ntp_global: config: peers: - peer: "{{ item }}" version: 2 loop: "{{ ntp_server }}" ``` ### Playbook Explanation - **Play Definition**: The play is named "Configure NTP" and targets the `router` host group. The directive `gather_facts: false` disables the default fact-gathering behavior. - **Task Definition**: A single task is defined within the play. This task uses the `vars` keyword to define a list of NTP servers. - **Task Details**: - **Task Name**: "Configure NTP on Router" - **Variable Definition**: The `ntp_server` variable is defined as a list of four IP addresses. - **Module**: The `cisco.ios.ios_ntp_global` module configures NTP settings on Cisco IOS devices. - **Configuration**: The `config` parameter specifies the NTP peers to be configured, using a loop to iterate over the `ntp_server` list. - **Loop**: The `loop` keyword iterates over the `ntp_server` list, configuring each NTP server in turn. ### Understanding `item` in the Loop In Ansible loops, `item` represents the current element in the list being processed. As the loop iterates over the `ntp_server` list, `item` holds the value of each NTP server IP address one by one. For example: - During the first iteration, `item` is `1.1.1.1`. - During the second iteration, `item` is `2.2.2.2`. - And so on for `3.3.3.3` and `4.4.4.4`. This allows the task to apply the configuration for each NTP server individually. ### Running the Playbook To execute the playbook, you would use the following command: ```bash ansible-playbook ntp_config.yaml ``` ### Playbook Output The playbook output might resemble this: ```plaintext PLAY [Configure NTP] ******************************************************************* TASK [Configure NTP on Router] ********************************************************* changed: [172.16.10.14] => (item=1.1.1.1) changed: [172.16.10.14] => (item=2.2.2.2) changed: [172.16.10.14] => (item=3.3.3.3) changed: [172.16.10.14] => (item=4.4.4.4) PLAY RECAP ***************************************************************************** 172.16.10.14 : ok=1 changed=1 unreachable=0 failed=0 skipped=0 ``` ### Analysis of Playbook Output - **Play Execution**: The play named "Configure NTP" begins execution. - **Task Execution**: The task "Configure NTP on Router" executes for each item in the `ntp_server` list. - For each IP address in the `ntp_server` list, a configuration change is applied to the router. - The output confirms successful configuration changes for each NTP server. - **Play Recap**: The play recap summarizes the execution: - `ok=1`: One task executed successfully. - `changed=1`: The task made configuration changes. - `unreachable=0`: No hosts were unreachable. - `failed=0`: No tasks failed. - `skipped=0`: No tasks were skipped. This example demonstrates the use of loops in Ansible to efficiently configure multiple items, simplifying the management of network devices. ## Loop Through Device Information To process device information, we use the `ios_facts` module, which collects facts from a device running IOS. Here's how it works: ```yaml --- - name: "Playbook: Loop IP Addr" hosts: router gather_facts: false tasks: - name: "Get facts from device" cisco.ios.ios_facts: gather_subset: interfaces - name: "Print device information" ansible.builtin.debug: msg: "{{ ansible_facts['net_hostname'] }} has IP Addr {{ item }}" loop: "{{ ansible_facts['net_all_ipv4_addresses'] }}" ``` ### Playbook Explanation This playbook, named "Loop IP Addr," is designed to run on a host group named "router." The `gather_facts` option is set to `false` because we manually gather the necessary facts using the `ios_facts` module. #### Tasks 1. **Get facts from device** - The `cisco.ios.ios_facts` module is used to gather information from the device, specifically focusing on the `interfaces` subset. 2. **Print device information** - The `ansible.builtin.debug` module is used to print the device's hostname and its IP addresses. - The `loop` directive iterates over the list of IP addresses stored in `ansible_facts['net_all_ipv4_addresses']`. ### Understanding the Loop In the second task, the loop takes each IP address from the list `ansible_facts['net_all_ipv4_addresses']` and prints a message. The message includes the device's hostname and the current IP address (`{{ item }}`) from the loop. This way, each IP address of the device is printed along with the device's hostname. ``` PLAY [Playbook: Loop IP Addr] ********************************************************** TASK [Get facts from device] *********************************************************** ok: [172.16.10.14] TASK [Print device information] ******************************************************** ok: [172.16.10.14] => (item=9.9.9.10) => { "msg": "R1 has IP Addr 9.9.9.10" } ok: [172.16.10.14] => (item=172.16.10.14) => { "msg": "R1 has IP Addr 172.16.10.14" } ok: [172.16.10.14] => (item=192.168.71.139) => { "msg": "R1 has IP Addr 192.168.71.139" } ok: [172.16.10.14] => (item=1.1.1.1) => { "msg": "R1 has IP Addr 1.1.1.1" } PLAY RECAP ***************************************************************************** 172.16.10.14 : ok=2 changed=0 unreachable=0 failed=0 skipped=0 ``` As per documentation, we can modify the playbook: ```yaml --- - name: "Playbook: Loop IP Addr" hosts: router gather_facts: false tasks: - name: "Get facts from device" cisco.ios.ios_facts: gather_subset: interfaces - name: "Print device information" ansible.builtin.debug: msg: "{{ ansible_net_hostname }} has IP Addr {{ item }}" loop: "{{ ansible_net_all_ipv4_addresses }}" ``` This playbook demonstrates how to gather device information using the `ios_facts` module and print each IP address associated with a device. By utilizing the `debug` module and looping through the IP addresses, the playbook provides a clear and concise way to display critical network information for devices running IOS.