vpnc: add page (#2837)

pages/linux/vpnc.md

@@ -0,0 +1,11 @@
+# vpnc
+
+> A VPN client for the Cisco 3000 VPN Concentrator.
+
+- Connect to a defined configuration file:
+
+`sudo vpnc {{config_file}}`
+
+- Terminate the previously created connection:
+
+`sudo vpnc-disconnect`