Hi Artem,
The feature is called "Query Interface". You can configure it and even if ft vlan is down, standby will ping this interface (query) vlan and if this is UP, standby will not assume the role of ACTIVE.
Configuring a Query Interface
Configure a query interface to allow the standby member to determine whether the active member is down or if there is a connectivity problem with the FT VLAN. A query interface helps prevent two redundant contexts from becoming active at the same time for the same FT group. Before triggering a switchover, the ACE pings the active member to make sure that it is down. Configuring a query interface allows you to assess the health of the active member, but it increases switchover time.
To configure a query interface, use the query-interface command in FT peer configuration mode. The syntax of this command is:
query-interface vlan vlan_id
The vlan_id argument specifies the identifier of an existing VLAN. Enter an integer from 2 to 4094.
For example, to configure a query interface, enter:
host1/Admin(config-ft-peer)# query-interface vlan 400
To remove the query interface from the peer configuration, enter:
host1/Admin(config-ft-peer)# no query-interface vlan 400
http://www.cisco.com/c/en/us/td/docs/app_ntwk_services/data_center_app_services/ace_appliances/vA1_7_/configuration/administration/guide/admgd/redundcy.html#wp1013201
Regards,
Kanwal
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