Description:
LANCOM routers and access points provide the following mechanisms for monitoring lines and connections: LCP polling, Dead Peer Detection, and ICMP polling. This document describes where these mechanisms are configured and which parameters are available.


Requirements:



LCP polling (line control protocol):
LCP polling is configured at the following locations:

LANconfig: Menu Communication → Protocols → PPP list → <Remote site> → Time
  • The value entered is multiplied by the factor 10 to specify the polling interval.
  • The default value is 0, which disables LCP polling.
  • The number of Retries is specified in the field below it.


Command line: Path /Setup/WAN/PPP/
  • The command set <remote site name> {Time} <value> is used to enter or change a value (e.g. set TEST {Time} 3).
  • The value entered is multiplied by the factor 10 to specify the polling interval.
  • The number of retries is is set with the command set <remote site name>{Try} <value> (e.g. set TEST {Try} 10).



ICMP Polling (Internet Control Message Protocol):
ICMP polling (ping) is configured at the following locations:

LANconfig: Menu Communication → Protocols → Polling table
  • Remote site to be monitored.
  • Target IP address(es) 1 to 4 (at least one IP address must be entered)
  • Time before retrying ICMP polling (every X seconds)
  • Number of retries, each 1 second apart

Process with a value of 40 seconds and 3 repetitions:
  • Creation of an ICMP Packet
  • Wait 40 seconds for an answer => Result: no response
  • 1st repetition
  • Wait 5 seconds for an answer
  • 2nd repetition
  • Wait 3 seconds for an answer
  • 3rd and last repetition
  • Wait 1 second for an answer

  • If the address 0.0.0.0 is entered as IP address 1, the DNS server assigned by the Internet service provider is used as the destination.
  • The time entered into the polling table defines the time interval between ping requests. If the value 0 is entered, then the standard value of 30 seconds applies. If no reply to a ping is received then the remote site will be checked in shorter intervals. The device then tries to reach the remote site once a second. The number of retries defines how many times these attempts are repeated. If the value 0 is entered, then the standard value of 5 retries applies.

The address 0.0.0.0 should not be entered as IP address, as DNS servers of Internet service providers often don't respond to a ping (ICMP request). In this case the Internet connection cannot be established or it is interupted!


Command line: Path /Setup/WAN/Polling-Table/

  • With the command set <remote site name> <IP address 1> <IP address 2> <IP address 3> <IP address 4> <Ping-Interval> <Retries> you can enter or change your values (e.g. set 1und1 8.8.8.8 {Time} 5 {Try} 2).


DPD (Dead Peer Detection):
Dead Peer Detection can be configured for VPN connections at the following locations:

LANconfig: Menu VPN → General → Connection list → <vpn connection name>
Dead Peer Detection can be specified for each VPN connection here. This prompts a DPD packet to be sent if no packet is received over the VPN tunnel for the specified amount of time. 

The minimum time value for the Dead Peer Detection is 30 seconds. If you configure a value that is less than 30 seconds, it is ignored and the default minimum value applies.


Sequence with a value of 60 seconds:
  • 60 seconds go by without receiving a packet
  • A DPD package is generated
  • Wait 60 seconds for response
  • 1st retry
  • Wait 10 seconds
  • 2nd retry
  • Wait 10 seconds
  • 3rd and final retry
  • Wait 10 seconds
  • Terminate the VPN connection


Command line: Path /Setup/VPN/VPN-Peers

  • The command set <vpn connection name> {DPD-Inact-Timeout} <value> is used to enter or change a value (e.g. set TEST {DPD-Inact-Timeout} 60).



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