Just to warn you, these concepts are from my own knowledge and how I came to understand how the ACE understands load balancing. Please refer to the full documentation on Cisco’s website.
To fully understand how the ACE works there are core areas to be familiar with:
- Server load balancing
The ACE works in terms of virtualization. Within virtualization you have different areas:
- Role-based access control
- Resource Classes
A context is an actual virtualized environment in the ACE. You can configure multiple contexts which are all divided and act as a single ACE appliance. Within each context you can apply policies, servers, serverfarms, interfaces and even different administration rules.
Within each context you can create multiple domains. Domains allow you to control user access to objects in a context. A user is an account you create to allow administration to resources defined within the domain which is associated to a context.
Role-based Access Control
Otherwise known as RBAC. A set of permissions assigned to users which gives them predefined roles for access.
You create resource classes and associate contexts to a resource class to manage access to ACE resources. This is useful for controlling how much resources can be used per context so that one context does not utilize all resources on the ACE. When all resources are exhausted you will have performance issues.
Define a resource class. When configuring an ACE you will start off in the Admin context. From there you will create a Resource Class for the virtual context(s) you will create to load balance your website.
Create a context. After a Resource Class is created and configured you create a Context and associate it with a Resource Class. This context will serve as the virtual ACE which will manage traffic to the site you want load balanced.
By default, traffic to the newly created context is denied so you will have to create an access list to allow traffic. (Later described)
To begin configuring load balancing you will have to define an rserver. An rserver is a “Real Server”. This maps back to your web server. rservers host the same content which is why we’re load balancing, right?
Those rservers will be associated with a serverfarm. A server farm is a group of networked real servers (rservers).
So in summary and for simplicity, you would configure the ACE in this manner:
- Resource Class
- Real Servers
- Server Farm
That’s just a quick rundown on configuring an ACE. Also, when configuring Contexts, you must specify how traffic will exit so a default route will need to be configured.