Traditionally, a firewall is a routed hop and acts as a default gateway for hosts that connect to one of its screened subnets. A transparent firewall, on the other hand, is a Layer 2 firewall that acts like a “bump in the wire,” or a “stealth firewall,” and is not seen as a router hop to connected devices
Basic config on ASA : convert ASA to transparent (this will wipe all the config on the ASA).
BB-FW(config)# firewall transparent
Configure interface in respected VLAN
BB-FW(config)# interface Gig 1/1
BB-FW(config-if)# switchport access vlan 100
BB-FW(config-if)# no shutdown
BB-FW(config-if)# interface Gig 1/4
BB-FW(config-if)# switchport access vlan 200
BB-FW(config-if)# no shutdown
Configure VLAN in to respected inside and outside, and add them to bridge group.
BB-FW(config-if)# interface vlan 100
BB-FW(config-if)# nameif outside
BB-FW(config-if)# bridge-group 1
BB-FW(config-if)# interface vlan 200
BB-FW(config-if)# nameif inside
BB-FW(config-if)# bridge-group 1
ASA can be managed using BVI as below IP address :
BB-FW(config-if)# interface bvi 1
BB-FW(config-if)# ip address 192.168.100.254
Basic ACL to test :
access-list outside-in extended permit icmp any any echo-reply
access-list outside-in extended permit icmp any any unreachable
access-list outside-in extended permit icmp any any traceroute
access-list outside-in extended permit icmp any any time-exceeded
access-list outside-in extended permit udp any any eq domain
Happy labbing………………!