The rlm_acct_unique module creates a unique accounting session Id.

Many NAS vendors have their equipment supply an Acct-Session-Id attribute which is not unique over reboots. This makes accounting difficult, as there will be many independent sessions with the same Acct-Session-Id attribute. This module uses the Acct-Session-Id attribute, along with other attributes in the request, to create a more unique session ID, called Acct-Unique-Session-Id.

The main configuration items to be aware of are:


A list of the attributes used in calculating an MD5 hash which is used as the value for the unique session id.


modules {

  acct_unique {

	key = "User-Name, Acct-Session-Id, NAS-IP-Address, NAS-Port"





preacct {



After generating the MD5 hash, the module adds it to the accounting request packet received from the client. It will look something like this in your detail file:

Acct-Unique-Session-Id = "c66ef57e480b9d26"

NOTE: Any attribute you specify that is not found in the 'dictionary' file will cause the server to fail and exit with an error.

NOTE: If you want the Acct-Unique-Session-Id of the Start and the Stop packet of a particular session to match, you must use values for the key that will stay the same for the Start and Stop. The above example is a good start. Adding 'Acct-Session-Time', for example, would cause a mismatch because that value is not the same on the Start and Stop accounting packets.


authorization, pre-accounting, accounting



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Chris Parker, [email protected]