FlexConnect Smart AP image upgrade

Scene Introduction

In a network operations lab at SubnetBits, Professor Network is sitting at a table full of wireless devices, explaining to Sophie, who joins him, the process of upgrading Cisco AP images running in FlexConnect mode.

Smart AP image upgrade Introduction

Hello Professor, seeing all this wireless equipment reminds me of last month when we had to upgrade multiple switches in our Data Center. It made me curious about how we efficiently upgrade Cisco FlexConnect AP images in branch offices with hundreds of APs. Do we have to upgrade each AP individually?

Actually, Sophie, it’s more efficient than that. The FlexConnect APs don’t need to be upgraded individually. Instead, they download their new image from the Wireless LAN Controller via the WAN link. This centralized approach simplifies the upgrade process, especially in branch offices with numerous APs, by avoiding the need to manually update each one.

Hmmm, so If we have tens or hundreds of APs in our branch locations, wouldn’t the WAN link become congested since all these APs will download their image from the WLC?

Sophie, FlexConnect APs use a smart upgrade process to reduce WAN bandwidth usage and upgrade time. Here’s how it works:

Primary AP Download: Initially, one AP per model, in each Site Tag, is elected as primary and downloads the new image from the controller over the WAN. If the primary AP is not selected manually, the AP with the lowest MAC address will become the Primary AP.
Subordinate APs Upgrade: This primary AP then acts as a server to other APs of the same model in the local network. These subordinate APs download the image from the primary AP using TFTP, significantly reducing the WAN load.
Concurrent Downloads: Up to three subordinate APs can download the image simultaneously from the primary. If more APs try to download at once, they use a random back-off timer to retry later.

Question Professor: For every AP model one primary AP will be elected?

Great question Sophie, and the answer is: it depends on the code running. In previous versions of code, the APs had to be exactly the same, but today, the APs just need to be in the same family. Here are the AP families and the images they share:

AP families sharing the same image:
1. ap3g3: Aironet^® 4800, 3800, 2800, 1560 Series
2. ap1g5: Aironet 1815i, 1815w, 1815m, 1540, 1840 Series
3. ap1g4: Aironet 1852, 1832
4. ap1g7: Catalyst 9115AX, 9120AX Series
5. ap1g6: Catalyst 9117AX Series
6. ap1g6a: Catalyst 9130AX Series

So, this method streamlines the upgrade process across multiple APs while conserving network resources?

Exactly. It’s a more efficient way to handle upgrades, especially in environments with numerous APs and limited WAN bandwidth.

And how is this configured?

In the AireOS interface, you navigate to the FlexConnect Groups section, select the group, and configure the Smart AP Upgrade feature. You choose the primary AP, set the maximum retry count for downloading the image, and select the upgrade image type. Below, I’ve prepared the necessary steps to configure FlexConnect Smart AP Image Upgrade on AireOS. I’ve also include 3 slides in order for you to visualize the configuration steps.

AireOS Smart AP Image Upgrade Configuration

Step 1	Navigate to Wireless > FlexConnect Groups on the controller.
Step 2	Select the desired FlexConnect Group.
Step 3	Go to the Image Upgrade tab.
Step 4	Enable the FlexConnect AP Upgrade option by checking the box.
Step 5	Set the Slave Maximum Retry Count and select the upgrade image (Primary, Backup, or Abort). Slave Maximum Retry Count is the number of times a subordinate AP tries to download the upgrade image from a primary AP. If the download fails after these attempts, the upgrade occurs over the WAN, from the controller. The default setting is 44 retries, with a range from 1 to 63.
Step 6	Assign a primary AP for the upgrade using the AP Name drop-down and click Add Master.
Step 7	Apply your settings.
Step 8	Click FlexConnect Upgrade to upgrade.

Step 1 - Click on Wireless tab and after that click on FlexConnect Groups.

Step 2 - Click on the desired FlexConnect group.

Step 3 - Click on Image Upgrade tab and check the box for FlexConnect AP Upgrade

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That seems like a practical solution for large-scale deployments.

Indeed, it’s essential for efficient network management and minimizing downtime during upgrades.

How about the WLCs that run on IOS XE? Are the configuration steps the same?

Sophie, the key difference lies in how they manage the upgrade process. In AireOS Smart AP Image Upgrade, you manually select a primary AP for each model in a FlexConnect group. Recall that if the Primary AP is not manually selected, the one with the lowest MAC will be dynamically chosen. This primary AP downloads the image and serves it to subordinate APs in the group.

On the other hand, IOS XE Efficient Image Upgrade is more automated. An AP per model is dynamically chosen as the primary AP. It downloads the image from the controller and then serves it to a maximum of three subordinate APs per model. This reduces WAN latency and makes the upgrade process more efficient and less reliant on manual configuration.

In IOS XE, the Efficient Image Upgrade is enabled by default under every Flex Profile. Below are the steps to get to this configuration.

IOS XE Efficient Image Upgrade Configuration

Step 1	Navigate to Configuration > Tags & Profiles > Flex.
Step 2	Click on Add to add a new Flex Profile.
Step 3	Efficient Image Upgrade is enabled by default.

Step 1 - Click on Configuration > Tags & Profiles > Flex

Step 3 - Efficient Image Upgrade is enabled by default

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Thank you, Professor, for the detailed explanation on Smart AP and Efficient Image Upgrade. It really clarifies how we can efficiently manage our APs’ firmware updates, especially in branch offices.