Apply Access Control Lists (ACLs) for Management Access

Restrict SSH/Telnet management to authorized IP ranges only:

   #ip access-list standard MGMT_ACCESS
   #permit <Authorized_MGMT_Subnet>
   #deny any
   #line vty 0 4
   #access-class MGMT_ACCESS in
   #transport input ssh

Disable Telnet if not required:

   #line vty 0 4
   #transport input ssh