Using two interfaces:Configure primary first.
On the primary
failover
failover lan unit primary
failover lan interface LFAIL GigabitEthernet0/6
failover key cisco1
failover replication http
failover link LSTATE GigabitEthernet0/7
failover interface ip LFAIL 172.20.248.17 255.255.255.252 standby 172.20.248.18
failover interface ip LSTATE 172.20.248.21 255.255.255.252 standby 172.20.248.22
monitor-interface INSIDE <- if not physical on the secondary failover lan unit secondary failover lan interface LFAIL GigabitEthernet0/6 failover key cisco1 failover interface ip LFAIL 172.20.248.17 255.255.255.252 standby 172.20.248.18 failover Using management interface with Vlans.
interface Management0/0
!
interface Management0/0.303
description LAN Failover Interface
vlan 303
!
interface Management0/0.304
description STATE Failover Interface
vlan 304
failover
failover lan unit primary
failover lan interface LAN-FO Management0/0.303
failover key cisco1
failover link STATE-FO Management0/0.304
failover interface ip LAN-FO 192.168.2.37 255.255.255.252 standby 192.168.2.38
failover interface ip STATE-FO 192.168.2.41 255.255.255.252 standby 192.168.2.42
On the secondary unit.
failover lan unit secondary
failover lan interface LAN-FO Management0/0.303
failover key cisco1
failover interface ip LAN-FO 192.168.2.37 255.255.255.252 standby 192.168.2.38
failover