FortiNAC, FortiGate and FortiAP - CoA request fail with "Session Context Not Found"

[Mike77]

Hi Guys

I'm testing FortiNAC with a FortiGate (as a wireless controller) and FortiAP's.

During testing, I noticed that coa does not work as desired. The VLAN is only changed during disconnect/connect of the client.

I use the command "sendcoa -ip 172.xx.xx.xx -mac XX:XX:XX:XX:XX:XX -dis" on FortiNAC.

With "execute tcpdump -i any port 3799 -v" I get the following output:

tcpdump: data link type LINUX_SLL2
dropped privs to admin
tcpdump: listening on any, link-type LINUX_SLL2 (Linux cooked v2), snapshot length 262144 bytes
10:44:49.640276 port1 Out IP (tos 0x0, ttl 64, id 43159, offset 0, flags [DF], proto UDP (17), length 78)
s-test-fncesx01.42844 > _gateway.3799: RADIUS, length: 50
Disconnect-Request (40), id: 0x25, Authenticator: aafde2cc1e57197d88bdfac5632f91ab
Calling-Station-Id Attribute (31), length: 19, Value: XX:XX:XX:XX:XX:XX
User-Name Attribute (1), length: 11, Value: host/XXXX

10:44:51.641526 port1 In IP (tos 0x0, ttl 64, id 3676, offset 0, flags [none], proto UDP (17), length 78)
_gateway.3799 > s-test-fncesx01.42844: RADIUS, length: 50
Disconnect-NAK (42), id: 0x25, Authenticator: c433a7cf357955e717cc13daf18e461c
Error-Cause Attribute (101), length: 6, Value: Error cause 503: Session Context Not Found
Event-Timestamp Attribute (55), length: 6, Value: Thu Sep 11 10:44:49 2025
Message-Authenticator Attribute (80), length: 18, Value: .0..j?a.u.....m.

Under "CLIENT EXTENDED ATTRIBUTES" I see only attribute 1 and attribute 31

(Command: "client -mac XX:XX:XX:XX:XX:XX")

If I interpret the page correctly https://community.fortinet.com/t5/FortiAP/Troubleshoot-Tip-Most-common-causes-CoA-request-fail-to/ta... it says, attribute 8 is missing.

Any idea how I can fix that?

[ebilcari]

Was the host connected and authenticated (active session) when you have tried the manual send of the CoA/DM?

To have more information you can also enable the following debug from the FGT side:

# diagnose debug application radius_das 8