Use this procedure to configure FA message authentication on an interface (port or MLT).
enable
configure terminal
interface GigabitEthernet {slot/port[/sub-port][-slot/port[/sub-port]][,...]} or interface mlt <1-512>

Note
If the platform supports channelization and the port is channelized, you must also specify the sub-port in the format slot/port/sub-port.
[default] [no] fa message-authentication

Note
When FA is enabled, message authentication is enabled by default. The authentication key is set to the default value and displays encrypted on the output.
Switch:1>en Switch:1#conf t Enter configuration commands, one per line. End with CNTL/Z. Switch:1(config)#
Enable message authentication on a port.
Switch:1(config)#interface gigabitEthernet 1/2
Switch:1(config-if)#fa message-authentication
Switch:1(config-if)#show fa interface port 1/2
==================================================================
                            Fabric Attach Interfaces
==================================================================
INTERFACE    SERVER   MGMT     MGMT     MSG AUTH MSG AUTH  ORIGIN  
             STATUS   ISID     CVID     STATUS   KEY         
------------------------------------------------------------------
Port1/2      enabled  0        0        enabled  ****        
------------------------------------------------------------------
 1 out of 1 Total Num of fabric attach interfaces displayed
------------------------------------------------------------------
Switch:1(config-if)#exit
Switch:1(config)#
Enable message authentication on an MLT.
Switch:1(config)#interface mlt 10
Switch:1(config-mlt)#fa message-authentication
Switch:1(config-mlt)#show fa interface mlt 10
===================================================================
                            Fabric Attach Interfaces
===================================================================
INTERFACE    SERVER   MGMT     MGMT     MSG AUTH MSG AUTH   ORIGIN        
             STATUS   ISID     CVID     STATUS   KEY            
-------------------------------------------------------------------
Mlt10        enabled 0        0         enabled  ****          
-------------------------------------------------------------------
 1 out of 1 Total Num of fabric attach interfaces displayed
-------------------------------------------------------------------
Switch:1(config-mlt)#exit
Switch:1(config)#
The following example demonstrates disabling message authentication on a port or MLT.
Switch:1(config)#interface gigabitEthernet 1/2
Switch:1(config-if)#no fa message-authentication
Switch:1(config-if)exit
Switch:1(config)
Switch:1(config)#interface mlt 10
Switch:1(config-mlt)#no fa message-authentication
Switch:1(config-mlt)#show fa interface 
 
===================================================================
                            Fabric Attach Interfaces 
===================================================================
INTERFACE    SERVER   MGMT     MGMT     MSG AUTH MSG AUTH   ORIGIN           
             STATUS   ISID     CVID     STATUS   KEY               
-------------------------------------------------------------------
Port1/2      enabled  0        0        disabled ****              
Mlt10        enabled  0        0        disabled ****              
-------------------------------------------------------------------
2 out of 2 Total Num of fabric attach interfaces displayed
-------------------------------------------------------------------