I have decided to use Vlan 10 and 30 as primary for BRAS-1, Vlan 20 and 40 as primary for BRAS-2. Note: in this LAB, AC’s are labelled BRAS-1 and BRAS-2.
In this scenario, we are using a switch configured to define a single Vlan to the PPPoE-Client and trunk all Vlans to the AC. This LAB is intended to show the mechanism to provide HA fail-over between two AC’s, not the different types of transport from which we get client traffic to the AC. With this in mind, we will take the following drawing taken from my EVE-NG lab which I used to create this. You also wish to load balance between the two AC’s as best as possible while still providing the fail-over between each should one fail. You currently only have one active AC/BRAS servicing your client connections and wish to add a second, preferably in an active/active redundant method. In this article I am going to lay out the foundation and solution to achieve AC load balancing.
When you introduce a second (or third, fourth etc.) AC for an active/standby or active/active solution, it is often unclear how to load balance PPPoE sessions across multiple AC’s. With this type of connection working at layer 2, the PPPoE client and AC obviously must have a Layer 2 adjacency in order to form the link.Īs consultants, we are asked quite frequently how we design and implement redundancy when using PPPoE as a client termination method.
If configured to authenticate using AAA, it will send a request and await a response and then act accordingly. The function of the AC is to negotiate the link parameters between itself and the client and then pass any specific properties to the client.ĭuring this, the AC will check its local database to see if the client credentials exist, username/password combination. Connections initiated from a client terminate on what is known as a BRAS (Broadband Remote Authentication Server), or Access Concentrator (AC) from herein. PPPoE is a layer 2 connection protocol widely used in service provider networks. For the purpose of this article though, I will be sticking to a very specific problem that arises how to build redundancy when using PPPoE. Within this process lies several other moving parts, if you would like to read more you can visit this wiki page which explains PPPoE rather well ( ). The protocol itself resides at the data link layer (OSI Layer 2) and provides control mechanisms between the connection endpoints. Often used with a AAA system such as RADIUS, the ability to authenticate, authorize and account for customer connections made the use of PPPoE so appealing. Traditionally, PPPoE was used in DSL deployments but became one of the most adopted forms of customer device authentication in many networks. One of the most widely used protocols for authentication of user connections is PPPoE (or Point-to-Point over Ethernet).
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