Configure Aruba Switch NTP (GNS3 Lab)

This guide covers how to configure NTP (Network Time Protocol) on an Aruba switch and, as a bonus, how to install and configure an NTP server on an Ubuntu system. This ensures your network devices maintain accurate time synchronization.

Step 1: Aruba Switch Initial Setup

In this lab environment (GNS3), we start with a factory-reset Aruba switch. First, we must configure basic connectivity so the switch can talk to the Ubuntu server.

1. Login and Interface Configuration

Log in with the username admin (default password is blank). Configure the interface connected to the server (e.g., interface 1/1/1). Disable routing on the interface (default for this image) and enable it:

interface 1/1/1
 no routing
 no shutdown
 exit

2. Configure VLAN and IP

Next, assign an IP address to VLAN 1 to establish network connectivity.

interface vlan 1
 ip address 172.16.1.3/24
 exit

3. Test Connectivity

Verify that the switch can reach the Ubuntu server (IP 172.16.1.10) using ping:

ping 172.16.1.10

If the ping is successful, we have confirmed connectivity.

Step 2: Configure NTP on the Aruba Switch

By default, the switch may be configured to use pool.ntp.org. We want to point it to our local Ubuntu server instead.

[Image of network diagram showing NTP synchronization flow between a client switch and an NTP server]

1. Remove Default NTP Server

Check the current configuration with show running-config. To remove the default server, copy the configuration line and prepend no:

no ntp server pool.ntp.org

2. Add Local NTP Server

Add the IP address of your Ubuntu server. Using the iburst option is recommended as it allows for faster initial synchronization.

ntp server 172.16.1.10 iburst

Step 3: Install NTP Server on Ubuntu (Chrony)

Now we move to the Ubuntu server to configure it as the time source. We will use Chrony, which is the default NTP implementation for modern Ubuntu versions.

1. Install Chrony

Connect to your server via SSH and elevate to root. Update your repositories and install Chrony if it is not already present.

apt update && apt upgrade -y
apt install chrony -y

2. Configure Chrony

Edit the configuration file located at /etc/chrony/chrony.conf.

**Upstream Pool:** You can change the default pool to a local one (e.g., se.pool.ntp.org for Sweden) to reduce latency.
**Allow Subnet:** You must explicitly allow the subnet of your network devices to query the server. Uncomment or add the allow directive:

allow 172.16.1.0/24

3. Restart and Verify

Save the file and restart the service to apply changes:

systemctl restart chrony
systemctl status chrony

You can also check the synchronization status of the server itself using:

chronyc tracking

Step 4: Verify Synchronization on Aruba Switch

Return to the Aruba switch console to confirm it is receiving time from the Ubuntu server.

1. Check NTP Associations

Run the command show ntp associations. You are looking for the "Reach" value to increase (eventually hitting 377) and the state to become synchronized.

show ntp associations

If you recently changed the time manually, it may take 3 to 5 minutes to resynchronize.

2. Set Time Zone

To ensure the displayed time is correct for your region, configure the time zone:

clock timezone europe/stockholm

3. Final Verification

Use show clock to see the final, synchronized time and date.

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