In some rare cases, VPN Tunnels hang-up randomly and needs to be bounced or restarted to restart the VPN Tunnel negotiate that on some cases the easiest fix on VPN Down issues
Check Phase 1 Status of the Tunnel:
show crypto ipsec sa
Normal/UP status should show: QM_IDLE (More info on Status here)
Restarting VPN Tunnel
If you have multiple VPN Tunnels, Identify the peer IP of the tunnel you wish to Restart.
Usually, you can associate the ACL or IPSEC Policy that calls the peer IP and the
EXAMPLE:
crypto map CUSTOMER-VPN 24 ipsec-isakmp
description Customer24
set peer 122.122.122.122
set transform-set TR-3DES-SHA 256
match address VPN-Customer24
Restart the Tunnel:
clear crypto sa peer 122.122.122.122 (Clear all SAs for given crypto peer)
or
clear crypto session remote 122.122.122.122 (Clear crypto sessions for a remote IKE peer)
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