Hello I have five C3850. they have all the same configuration (except port configuration).  I manage them trough the management interface gi0/0 I authenticate with a Radius   On all the switches, i have configured Radius authentication . The authentication configuration is excactly the same on all the switches (see below the configuration). HOWEVER, on two of them, they can't contact the radius server when i autheticate, and i wonder why !!!!   Of course i have tested that the switches can contact the radius server with this command : ping vrf Mgmt-vrf 10.10.0.111 I have also test that there is no issue with firewall an this test is not rejected : telnet 10.10.0.111 1812 /vrf Mgmt-vrf   End, i have monitored the traffic on gi0/0 of failed switches and i note that when i try to authenticate there is no traffic going out the gi0/0 to reach the radius server (wheras on non failed switch the traffic is gouing ou the interface)   To resume : i have the feeling that event if they have the same configuration that the others, two switches don't send radius traffic trough the gi0/0 interface   Thank you for your help or suggestions   ------ CONFIGURATION -------   aaa new-model ! aaa authentication login default group radius local aaa authorization exec default group radius local if-authenticated aaa session-id common interface GigabitEthernet0/0 description management vrf forwarding Mgmt-vrf ip address 10.11.87.24 255.255.0.0 speed 1000 negotiation auto ip route vrf Mgmt-vrf 10.10.0.0 255.255.0.0 10.11.0.254 ip route vrf Mgmt-vrf 10.16.0.0 255.255.0.0 10.11.0.254 radius server XXXX address ipv4 10.10.0.111 auth-port 1812 acct-port 1813 key 7 zzzzzzzzzz     ... View more