F5 Distributed Cloud Customer Edge Migration Centos to RHEL

In this article, I will introduce a process to migrate a Customer Edge site from End of Life Centos OS to RHEL Operating System.

Introduction:

Back in December 2023, F5 Distributed Cloud Customer Edges image was based on Red Hat Enterprise Linux or RHEL. Operating System Prior to that the Customer Edge ran on Centos 7.x Operating System, which has been announced End of Life . In this article, I will provide a migration strategy from Centos to RHEL OS for customer edge sites that are in a SaaS-Hybrid Edge Deployment pattern (#2 in the slide below) where the VIP is on the Regional Edge and the tunnel termination and SNAT are on the customer edge. While we are using this deployment pattern as an example, the concepts for other patterns are the same with a few caveats which I will include at the end of this article.

High-Level Concepts:

Before we discuss the migration phases, I want to introduce a few concepts that we will be utilizing. The first concept is what we call a Virtual Site. A virtual Site provides us the ability to perform a given configuration on set (or group) of Sites. The second term is Origin Pool. An origin pool is a mechanism to configure a set of endpoints grouped together into a resource pool used in the load balancer configuration.

The typical CE Site deployment consists of a HA cluster that discovers endpoints via a origin pool picked via the CE Site. This discovery is typically via Private DNS or RFC-1918 IP ranges, all though other methods are available. When we introduce the virtual site construct we will perform this discovery via a "Virtual Site" and not the original "CE Site". As depicted below on the right hand side of the drawing, you will see the origin pool is now discovered from all 6 nodes in the virtual site and will route traffic to the endpoint per the LB algorithm.

Also, the Virtual Site construct can be utilized for more advanced HA design scenarios and even for additional bandwidth between RE and CE, but this will be discussed in other articles.

Virtual Site Setup:

Perquisites:

Current Centos Customer Edge Site.
New RHEL OS Customer Site

We first start to setup the virtual site construct by logging into our Distributed Cloud tenant. Once logged in:

Navigate to "Shared Configuration"
Under "Manage" chose "Virtual Site"
Provide a Name, Description, Site Type (in this case CE), and a Site Expression
Once the Virtual Site label is created, we navigate to the existing Centos CE Cluster and add the Site Expression that we created in previous step to the site Labels section
Goto Multi-Cloud Network Connect tile
Goto "Manage"
"Site Management" and choose the Site, Cloud Deployment site, or Secure Mesh Site. This will depend on how and where the site was deployed.
Once you have the correct site click on the 3 ellipses at the right and go to Manage Configuration and Edit

Add virtual Site Label

Type in the Key from “Site Selector Expression” my example is ”netta-az-vsite” and click Assign a Custom Key ‘netta-az-vsite’
Type in Value from “Site Selector Expression” my example is ”true” and click Assign a Custom Key ‘true’
Proceed with adding this same label to all sites that will be in the virtual site.

Virtual Site Origin Pool Configuration:

Now that we have our virtual site configured, we need to configure the origin pool and discover from the virtual site.

Go to Multi-Cloud Application Connect
In origin pool configuration choose the discovery method, IP or DNS of Origin on given sites
Under Site or Virtual Site, choose Virtual Site and pick your virtual site from drop-down:
Choose the "Virtual Site" configured in the previous step.
Rest of config should be the same

Validate origin is successfully discovered from newly created Virtual Site.

Go to HTTP LB Performance
Click on Origins Servers and you should see 2 origins, one form each site (centos and rhel) in virtual site

Migration:

Now that we have the virtual site and the virtual site origin pool discovery method built, we can start the migration.

Goto the HTTP LB and add the additional virtual site origin pool under the Origins section
Leverage weights and Priorities with the 2 origin pools to start the migration from the Centos Site to the Virtual site origin pool. Typical starting point is both origin pools will have a Priority of 1 and Weight will be in a value to equal 100. SO Centos origin pool has a weight of 95 and Virtual Site Origin Pool 5 and decrement and increment both as you migrate.
Once 100% of traffic is on the Virtual site origin pool remove the Virtual Site label from the centos site.
Remove the original Centos Site origin pool form the HTTP LB
Delete the Centos Cluster

Additional Info:

In the above example for the Customer Edge (CE) deployment, we were leveraging the RE's to publish VIPs to the internet and the CE's were used as tunnel termination points as well as SNAT to origin members. If you move the VIP to the CE there are a few caveats with the way to advertise that VIP to the network. For example to leverage all nodes within the cluster, you will need to provide a VIP Advertisement policy that consisted of an out-of-band DNS LB option or nested LB option.

Also as mentioned earlier in this article there can also be HA and bandwidth advantages to leveraging virtual sites as depicted below in the last slide.