Hi , Root!!!
Sao mình làm giống như bạn ở bước 2 và ping 8.8.8.8 không ra được Internet zậy!!!

ASA# sh run
ASA# sh running-config
: Saved
:
ASA Version 8.4(2)
!
hostname ASA
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
names
!
interface GigabitEthernet0
 nameif outside
 security-level 0
 ip address 200.0.0.1 255.255.255.0
!
interface GigabitEthernet1
 nameif inside
 security-level 100
 ip address 192.168.20.1 255.255.255.0
!
interface GigabitEthernet2
 nameif dmz
 security-level 50
 ip address 172.16.10.1 255.255.255.0
!
interface GigabitEthernet3
 shutdown
 no nameif
 no security-level
 no ip address
!
interface GigabitEthernet4
 shutdown
 no nameif
 no security-level
 no ip address
!
interface GigabitEthernet5
 shutdown
 no nameif
 no security-level
 no ip address
!
ftp mode passive
pager lines 24
mtu outside 1500
mtu inside 1500
mtu dmz 1500
icmp unreachable rate-limit 1 burst-size 1
no asdm history enable
arp timeout 14400
route outside 0.0.0.0 0.0.0.0 200.0.0.2 1
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00
timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00
timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute
timeout tcp-proxy-reassembly 0:01:00
timeout floating-conn 0:00:00
dynamic-access-policy-record DfltAccessPolicy
user-identity default-domain LOCAL
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart warmstart
telnet timeout 5
ssh timeout 5
console timeout 0
threat-detection basic-threat
threat-detection statistics access-list
no threat-detection statistics tcp-intercept
!
class-map inspection_default
 match default-inspection-traffic
!
!
policy-map global_policy
 class inspection_default
  inspect icmp
!
service-policy global_policy global
prompt hostname context
call-home reporting anonymous prompt 2
call-home
 profile CiscoTAC-1
  no active
  destination address http 
https://tools.cisco.com/its/service/oddce/services/DDCEService
  destination address email 
callhome@cisco.com
  destination transport-method http
  subscribe-to-alert-group diagnostic
  subscribe-to-alert-group environment
  subscribe-to-alert-group inventory periodic monthly
  subscribe-to-alert-group configuration periodic monthly
  subscribe-to-alert-group telemetry periodic daily
crashinfo save disable
Cryptochecksum:54152b0ca4857512294b957f72d79037
: end
Mô hình của mình đây!! 
 
Nhờ bạn giúp mình với!! gần 1 tháng này mình khổ vi cái đề tài này quá!!!
