This post describes how to configure two Cisco ASA’s in Active / Standby Fail-over configuration. The standby ASA will take over a failed unit.
Topology

Configuration: ASA-Primary
ASA-1# show run | begin fail failover failover lan unit primary failover lan interface Fail-Over GigabitEthernet0/0 failover link Fail-Over GigabitEthernet0/0 failover interface ip Fail-Over 192.168.0.1 255.255.255.0 standby 192.168.0.2 ! ! ASA-1(config)# failover ? lan - Specify the unit as primary or secondary or configure the interface and vlan to be used for failover communication ! ASA-1(config)# failover lan ? configure mode commands/options: interface Configure the interface and vlan to be used for failover communication unit Configure the unit as primary or secondary ! ASA-1(config)# failover lan unit ? configure mode commands/options: primary Configure the unit as primary secondary Configure the unit as secondary ! ASA-1(config)# failover lan unit primary ! ASA-1(config)# failover lan interface ? configure mode commands/options: WORD Specify the interface name ! ASA-1(config)# failover lan interface Fail-Over ? configure mode commands/options: WORD Specify physical or sub interface ! ASA-1(config)# failover lan interface Fail-Over Gi0/0 ! INFO: Non-failover interface config is cleared on GigabitEthernet0/0 and its sub-interfaces ! ASA-1(config)# failover ? link Configure the interface and vlan to be used as a link for stateful update information ! ASA-1(config)# failover link ? configure mode commands/options: WORD Specify the interface name ! ASA-1(config)# Failover link Fail-Over ? configure mode commands/options: WORD Specify physical or sub interface ! ASA-1(config)# Failover link Fail-Over Gi0/0 ! ASA-1(config)# failover ? interface Configure the IP address to be used for failover and/or stateful update information ! ASA-1(config)# failover interface ? configure mode commands/options: ip Configure the IP address and mask after this keyword ! ASA-1(config)# failover interface ip ? configure mode commands/options: Current available interface(s): Fail-Over Name of interface GigabitEthernet0/0 ! ASA-1(config)# failover interface ip Fail-Over ? configure mode commands/options: Hostname or A.B.C.D Specify the IP address Hostname/<0-128> or X:X:X:X::X/<0-128> Specify the IPv6 prefix ! ASA-1(config)# failover interface ip Fail-Over 192.168.0.1 255.255.255.0 ? configure mode commands/options: standby Configure the standby IP address after this keyword ! failover interface ip Fail-Over 192.168.0.1 255.255.255.0 standby 192.168.0.2 ! ASA-1(config)# failover failover Enable/disable failover feature ! ASA-1(config)# interface gigabitEthernet 0/0 ASA-1(config-if)# no shutdown ! ASA-1(config)# . No Active mate detected
Configuration: ASA-Secondary
ciscoasa(config)# failover lan unit secondary ciscoasa(config)# failover lan interface Fail-Over Gi0/0 INFO: Non-failover interface config is cleared on GigabitEthernet0/0 and its sub-interfaces ciscoasa(config)# failover link Fail-Over Gi0/0 ciscoasa(config)# failover interface ip FO 192.168.0.1 255.255.255.0 standby 192.168.0.2 ciscoasa(config)# interface gi0/0 ciscoasa(config)# failover ciscoasa(config)# . Detected an Active mate Beginning configuration replication from mate. WARNING: Disabling auto import may affect Smart Licensing Creating trustpoint "_SmartCallHome_ServerCA" and installing certificate... Trustpoint CA certificate accepted. WARNING: Trustpoint _SmartCallHome_ServerCA is already authenticated. End configuration replication from mate.
Verification:
ASA-1# show failover Failover On Failover unit Primary Failover LAN Interface: Fail-Over GigabitEthernet0/0 (up) Reconnect timeout 0:00:00 Unit Poll frequency 1 seconds, holdtime 15 seconds Interface Poll frequency 5 seconds, holdtime 25 seconds Interface Policy 1 Monitored Interfaces 0 of 61 maximum MAC Address Move Notification Interval not set Version: Ours 9.7(1), Mate 9.7(1) Serial Number: Ours 9APBRLWL1CL, Mate 9AUTVN4XK9E Last Failover at: 01:13:15 UTC Jan 14 2019 This host: Primary - Active Active time: 623 (sec) slot 0: empty Other host: Secondary - Standby Ready Active time: 0 (sec) Stateful Failover Logical Update Statistics Link : Fail-Over GigabitEthernet0/0 (up)