Configuration basic ASA 5505

Direccionamiento IP  

interface Vlan1                                          
 nameif inside                                            
 security-level 100                  
 ip address 192.168.20.1 255.255.255.0

interface Vlan2
 nameif outside
 security-level 0
 ip address dhcp setroute

interface Ethernet0/0
 switchport access vlan 2
no shutdown

interface Ethernet0/1
 switchport access vlan 1
no shutdown

Dynamic NAT / PAT Overload (ios 8.3 o posterior)

object network NAT
 subnet 0.0.0.0 0.0.0.0
 nat (inside,outside) dynamic interface

Aviltar DHCP

dhcpd dns 8.8.8.8
dhcpd address 192.168.20.5-192.168.20.100 inside
dhcpd enable inside

Aviltar acceso ASDM 

Preconfigure:

interface ethernet 0/1

nameif inside

configure:

username admin password cisco privilege 15

http server enable
aaa authentication http console LOCAL
http 192.168.20.0 255.255.255.0 inside
asdm image flash:/asdm-721.bin

Requriment for ASDM:
http://www.cisco.com/c/en/us/td/docs/security/asdm/7_1/release/notes/rn71.html