Problem with Kerberos auth on Web Gateway 9.2.8

[User17627912]

Greetings! Starting this week we experience issues with Kerberos authorization: users from specific subnets of our internal network (VPN specific) started to receive auth errors. Auth trace shows next errors: [2022-01-19 21:22:28.842 +03:00] debug logging has changed configuration for this file to: 'file:out=mwg-core__Auth.debug.log;options:file=append,multiline=yes,colored=no;threadids:ALL=yes;threadtypes:ALL=yes;plugins:ALL=0,Auth=8-9;classes:ALL=yes;fields:datetime=yes,binary=no,threadid=yes,threadtype=no,plugin=no,level=no,class=no,method=no,message=yes,source=no'. [2022-01-19 21:23:21.814 +03:00] [1227] Kerberos (1, 10.40.48.18) URL: https://www.googleapis.com [2022-01-19 21:23:21.814 +03:00] [1227] Kerberos (1, 10.40.48.18) Configuration: Kerberos Connection: 0x7f75d00ea5a0 RR: 0x7f7a4976acb0 [2022-01-19 21:23:21.814 +03:00] [1227] Kerberos (1, 10.40.48.18) Added authentication method: Negotiate [2022-01-19 21:23:21.814 +03:00] [1227] Kerberos (1, 10.40.48.18) Authentication didn't return values, failure ID: 4, authentication failed: 0 [2022-01-19 21:23:21.877 +03:00] [1230] Kerberos (2, 10.40.48.18) URL: https://www.googleapis.com [2022-01-19 21:23:21.877 +03:00] [1230] Kerberos (2, 10.40.48.18) Configuration: Kerberos Connection: 0x7f75d00ea5a0 RR: 0x7f7a49779db0 [2022-01-19 21:23:21.878 +03:00] [1230] Kerberos (2, 10.40.48.18) Incoming credentials: Negotiate TlRMTVNTUAABAAAAl4II4gAAAAAAAAAAAAAAAAAAAAAKAGFKAAAADw== [2022-01-19 21:23:21.878 +03:00] [1230] Kerberos (2, 10.40.48.18) Added authentication method: Negotiate [2022-01-19 21:23:21.878 +03:00] [1230] Kerberos (2, 10.40.48.18) Authentication didn't return values, failure ID: 0, authentication failed: 1 We have NTLM port listner also configured and it is working fine.