Day16.md

Day 16: Configuration Management - Replacing Configurations

Objective:

Understand how to completely replace the device's configuration using load_replace_candidate(). This is a more drastic change, so use with caution in production.

Concepts:

• load_replace_candidate(): Replaces the entire running configuration with the provided configuration.
• Caution: This can be destructive if not used carefully, as it removes any configuration not explicitly defined in the candidate.

Challenge:

Create a minimal configuration for arista1 that only includes a hostname and the management interface configuration, and apply it using load_replace_candidate(). Then, add back the loopback interface from Day 3.

Code Examples:

1. day4_replace_config.py:

from napalm import get_network_driver
import json
import time

DEVICE_IP = "YOUR_ARISTA1_IP"
USERNAME = "admin"
PASSWORD = "admin"

driver = get_network_driver("eos")
device = driver(
    hostname=DEVICE_IP,
    username=USERNAME,
    password=PASSWORD,
    optional_args={"secret": PASSWORD}
)

# Minimal replacement configuration
replace_config_initial = """
hostname arista-replaced
interface Management0
    ip address YOUR_ARISTA1_IP/24 # Adjust subnet as per your Containerlab setup
    no shutdown
"""

# Configuration to add back the loopback
add_loopback_config = """
interface Loopback1
    description "Managed by NAPALM - Added back"
    ip address 10.0.0.1/32
"""

try:
    device.open()

    print("\n--- Replacing configuration with minimal config ---")
    device.load_replace_candidate(config=replace_config_initial)
    diff_initial = device.compare_config()
    print(diff_initial)

    if diff_initial:
        print("\nCommitting initial replacement configuration...")
        device.commit_config()
        print("Initial replacement committed. Waiting a moment...")
        time.sleep(5) # Give the device time to apply

        print("\n--- Adding back Loopback1 ---")
        device.load_merge_candidate(config=add_loopback_config)
        diff_loopback = device.compare_config()
        print(diff_loopback)

        if diff_loopback:
            print("\nCommitting loopback configuration...")
            device.commit_config()
            print("Loopback configuration committed.")
        else:
            print("No loopback changes, discarding.")
            device.discard_config()
    else:
        print("No changes for initial replacement, discarding.")
        device.discard_config()

except Exception as e:
    print(f"Error: {e}")
    if device.is_alive():
        device.discard_config()
        print("Discarding candidate configuration due to error.")
finally:
    if device.is_alive():
        device.close()