Virtual Private Networks (VPNs) offer a way to securely connect different locations that are both connected to the Internet. Internet VPNs are way cheaper than private lines leased from a telco company, but unfortunately they are often much less reliable. Many times, when an Internet VPN “drops”, distant offices are no longer able to communicate — as network administrators, we want to know so we can fix it before our users notice anything!
This post shows one way to monitor site-to-site VPNs configured on a Cisco ASA firewall using SNMP and Nagios.