我是 IOS 的新手，我一直在 Packet Tracer 中构建配置文件。我仍然需要设置 NAT，因为我必须考虑几个流媒体。那么，我应该怎么做来配置这个路由器的安全部分？此配置是否使路由器保持开放状态？型号是 891F ISR，但我也会配置一些 881 路由器。

!
    hostname xxxxxxx
    !
    !
    !
    enable password secret xxxxxxxx
    !
    !
    ip dhcp excluded-address 192.168.1.1
    !
    ip dhcp pool LAN
     network 192.168.1.0 255.255.255.0
     default-router 192.168.1.1
     dns-server 8.8.8.8
    !
    !
    !
    username xxx privilege 15 password 0 xxxxxxxxxxx
    !
    !
    !
    !
    !
    ip ssh version 1
    ip domain-name cisco.com
    ip name-server 192.168.1.2
    !
    !
    spanning-tree mode pvst
    !
    !
    !
    !
    interface FastEthernet0/0
     description ISP connection
     ip address xxx.xxx.xxx.xxx 255.255.255.0
     duplex auto
     speed auto
    !
    interface FastEthernet0/1
     no ip address
     duplex auto
     speed auto
     shutdown
    !
    interface FastEthernet0/1/0
     switchport mode access
     spanning-tree portfast
    !
    interface FastEthernet0/1/1
     switchport mode access
     spanning-tree portfast
    !
    interface FastEthernet0/1/2
     switchport mode access
     spanning-tree portfast
    !
    interface FastEthernet0/1/3
     switchport mode access
     spanning-tree portfast
    !
    interface Vlan1
     ip address 192.168.1.1 255.255.255.0
    !
    ip classless
    ip route 0.0.0.0 0.0.0.0 xxx.xxx.xxx.xxx
    !
    !
    !
    banner motd ^CThis router is private property and may not be accessed without permission of the owner^C
    !
    !
    !
    !
    line con 0
     exec-timeout 0 0
     password xxxxxxxx
     logging synchronous
     login local
    line vty 0 4
     exec-timeout 0 0
     password xxxxxxx
     logging synchronous
     login local
    line vty 5 15
     exec-timeout 0 0
     password xxxxxxxxxxx
     logging synchronous
     login local
    !
    !
    !
    end