Linux and Cisco VPN Client “Remote peer is no longer responding”

I’m using the Cisco VPN client, and it seems unreliable on Linux – it occasionally connects but often just gives up with “Remote peer is no longer responding”.

Apart from the obvious firewall/nat checks [1][2], a solution seems to be to edit the .pcf file, bump up the timeout and force keepalives:

PeerTimeout=180
ForceKeepAlive=1