Core issue
This issue is due to the presence of Cisco bug ID CSCeg06605.
When Cisco IOS Software Release 12.2(18)SXD is used, the first RADIUS accounting request record is sent with source port zero instead of 1646 or 1813. This causes the first RADIUS response records from the RADIUS server to be dropped, as the response from the RADIUS server is sent with destination port zero. The reason is that the source port is set to 1646 by this command:
radius-server source-ports 1645-1646
However, the retransmission of the RADIUS accounting request is sent with the correct source port number, and the accounting transaction still succeeds. The first accounting request actually makes it to the RADIUS server. This is why the RADIUS server records two accounting start and two accounting stop records per session. This causes an accounting problem on the RADIUS server.
Resolution
In order to slightly reduce the impact of the problem, decrease the RADIUS server timeout value from five to two seconds with the radius-server timeout 2 command.
The fix for this bug is available in Cisco IOS Software Release 12.2(25)SEA.
Problem Type
Troubleshoot software feature
Product Family
Cisco Secure access control server
