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Description:

This document describes the monitoring function provided by the action table and notifications sent to the administrator via e-mail and/or SMS text message.
    Information:
    For notification via SMS, you need at least LCOS version 8.84 and a LANCOM 3G or 4G router.


Requirements:


Scenario:

The administrator should be notified of the failure of a VPN connection by e-mail. To perform this, the line is polled and an action is defined that sends an e-mail or SMS in the event of an unintended connection failure. In contrast, planned connection outages (e.g.: a forced re-connect of the DSL connection by the provider) should be ignored.

The monitoring by polling and the notification in case of disconnection only needs to be configured at the headquarters/central site. This will recognize the failure of any VPN connection and send information appropriately.

However, at least one of the remote sites should also be configured to send out a notification in case of DSL failure at the central site , as the central site would be unable to send out any e-mails.

Three types of polling are available with a LANCOM VPN router.
  • PPP LCP echo monitoring: This can be used when the link is a dynamic VPN connection over ICMP, when the link uses the ISDN D-channel or the ISDN B-channel.
  • Dead Peer Detection: Sends "are you there" packets as part of the IKE process.
  • ICMP polling: Sends ICMP packets to an IP address on the remote device (ideally the internal IP address of the remote VPN router).

It is possible to define several pollings to operate simultaneously. Only one type of polling has to be defined in order to recognize a connection failure.

The example scenario assumes a star-form VPN structure with three remote sites and one central site. The connections are established automatically by the remote sites (keep alive).




Headquarters: Network ID: 192.168.0.0/24 Local IP: 192.168.0.1
Remote site 1: Network ID: 192.168.1.0/24 Local IP: 192.168.1.1
Remote site 2: Network ID: 192.168.2.0/24 Local IP: 192.168.2.1
Remote site 3: Network ID: 192.168.3.0/24 Local IP: 192.168.3.1


Procedure:

The example shows how to use LANconfig to carry out the configuration for, in this case, the headquarters and remote site 1. When setting up other remote sites, the procedure at the headquarters remains the same.


1) Activating polling to monitor the VPN connection

This scenario uses DPD polling at both ends. This sends "Are you there" packets during the IKE at a configurable interval. It is activated by setting a time value for the Dead Peer Connection parameter in the connection list.



2) Configuring SMTP parameters

SMTP data are entered under Configuration -> Log & Trace -> SMTP Account.




3) Configuring the SMS module

If you are operating a 3G or 4G-capable LANCOM router with LCOS version 8.84 or later, you have the option to send notifications via SMS.

To do this, you configure the SMS module in the menu Configuration -> Log & Trace -> SMS messages.


  • Under Inbox size you set the maximum number of text messages stored in the device inbox. If the preset number is exceeded, the oldest message will be deleted. In this case there is no SYSLOG entry. The value 0 disables the limit, i.e. there is no limit on the number of messages stored.
  • The item Deletion of sent messages decides how the device handles sent text messages.
    • Immediately: Sent messages are not saved.
    • Never: Sent messages are saved permanently.
  • Under Outbox size you set the maximum number of text messages stored in the device outbox. If the preset number is exceeded, the oldest message will be deleted. In this case there is no SYSLOG entry. The value 0 disables the limit, i.e. there is no limit on the number of messages stored.
  • Under Syslog messaging you specify if and how the arrival of text messages is logged to the SYSLOG.
    • No: Incoming text messages are not logged to SYSLOG.
    • Only sender/no content: The arrival of a text message is recorded to the SYSLOG together with the sender's phone number.
    • Full: The arrival of a text message is recorded to the SYSLOG together with the sender's phone number and the message in full.
  • Optional: Under Mail forwarding address you specify the e-mail address to which the device forwards the incoming SMS text messages. E-mail routing will only work if a valid SMTP account is configured in the device (see step 2).


4) Time server configuration (NTP client)

The router must be configured as an NTP client of a time server in order to communicate the correct time of failure. In most applications this feature makes it easier to attribute the correct time of the log and monitoring.

For this purpose an NTP server can be specified under Configuration -> Date & Time -> Synchronization. The addresses of several popular NTP servers are already defined. Several addresses can be configured to acheive redundancy.




5) Generating a notification

The action table stores the connection status of the remote devices. An action specified here should be performed if there is no response to the polling.

5.1) Notification by e-mail

The syntax for the action is:

mailto:test@lancom.de?subject=VPN connection down at %t?body=VPN connection to Office 1 is down.
  • mailto: = command
  • test@lancom.de = target e-mail address
  • ? = separator
  • subject = subject line
  • %t = variable for current system time (optional)
  • body = text body






5.2) Notification by SMS

Information:
For notification via SMS, you need at least LCOS version 8.84 and a LANCOM 3G or 4G router.

The syntax for the action is:

exec: smssend -d <phone number> -t <text max. 160 characters>
  • Example: exec: smssend -d 017112345678 -t "The VPN connection to Office 1 is down."





6) Suppressing e-mail notification in the event of a forced disconnect of the underlying DSL link

Most DSL connections are subject to a forced re-connect every 24 hours. Perform the following steps to avoid an e-mail being generated for this event.

The forced re-connect is rescheduled to 3 AM using a real-time CRON job.

Command: do /other/manual/disconnect <remote_device_name>



Another CRON entry deactivates the action table entry used to generate the outage e-mail before the line is disconnected.

Command: set /setup/wan/action-table/X no

The placeholder X stands for the index entry in the action table (e.g., )set /setup/wan/action-table/1 no)



The action table is reactivated after the forced re-connection of the line.

Command: set /setup/wan/action-table/X yes

The placeholder X stands for the index entry in the action table (e.g., set /setup/wan/action-table/1 yes)