Q: 1. when does the IAP send the accounting request to the RADIUS servers?
2. I do not see any traffic from the client, still I see the accounting request was sent by the server. Why?
3. why was the accounting request sent x seconds after the authentication is complete?
A: 1. IAP will send the accounting request when it received first non-DHCP Layer-3 traffic from the client.
2. Sometimes due to ACLs in the role, the packets sent by the client will be dropped by the IAP. Thus there will be nothing in the datapath or uplink PCAPs. IAP will still send the accounting request as it received the non-DHCP Layer-3 traffic from the client.
3. Sometimes there is a delay in client getting connected and it getting an IP address from DHCP server. As the accounting request is only sent when non-DHCP Layer-3 traffic from client is received, delay in DHCP might cause delay in accounting requests.