Two possible ways to determine that (short of asking the sysadmin):

if your official VPN client is "Cisco Anyconnect", then OpenConnect should do the trick.
If your official VPN client is "Cisco VPN Client" (if I'm not mistaken), then vpnc should be used.

Another way (less effective): if you can open https://your-vpn-server
with a browser, there's a high probability that OpenConnect is the one you need. (please note the s in https!)