With version 2.7.31+, SmartMedia has the Associated server field in the RADIUS Client configuration page:

General Usage

Link accounting and authentication together logically

This allows to specify that whenever one of the two associated server is the Current one, then the other one should also be set as the current one.

So both servers have to be the 'current' at the same time.

Sends Acct/Auth requests to the same physical RADIUS server

The association resolves a problem when you would have two physical RADIUS servers, each server hosts an accounting and authorization server, and you have a limitation on the Radius server to run the primary accounting and authentication on the same server (identical IP).

A specific scenario

There are 2 Radius AUTH servers provisioned (RadSRV1 & RatSRV2) and 2 Radius ACCT servers provisioned (the same RadSRV1 & RadSRV2)

So there are 3 different possibilities for switchover:

1. SmartMedia will work with RadSRV1 as master for ACCT and AUTH
2. In case of external failure SmartMedia will switchover both stacks ACCT and AUTH to RadSRV2 
3. In some specific cases of external failures SmartMedia will switchover only one stack, so we will have AUTH to RadSRV1 and ACCT to RadSRV2:

• Either: AUTH to RadSRV1 and ACCT to RadSRV2
• Or: ACCT to RadSRV1 and AUTH to RadSRV2

In this case, associating the accounting and authentication to the same IP will prevent occurrence of scenario 3.