Hi suryakant,
Follow the below Link ,
https://supportforums.cisco.com/blog/150001/ipsec-vpn-redundancy-failover-over-redundant-isp-links
only primary link will work during normal case , when there is outage identified for primary link . Then automatically back link IP address will be active it will be listening ISKAMP request .
When you are configuring cisco VPN Client configure with backserver IP address (secondary IP address must be configured on backup server tab )
HTH
sandy