Application Note 34 Configuring ADSL to backup to PSTN/ISDN with automatic testing and recovery back to ADSL.
Contents 1 2 3 Introduction ............................................................................................................................................... 2 1.1 Outline ............................................................................................................................................... 2 1.2 Assumptions ...................................................................................................................................... 2 1.3 Corrections ...
Configuration: This Application Note assumes that the Digi Transport router is already configured with a working ADSL connection through PPP 1. 1.3 Corrections Requests for corrections or amendments to this application note are welcome and should be addressed to: uksupport@digi.com Requests for new application notes can be sent to the same address. 1.4 Version Version Number Status 1.0 Published 1.
2 CONFIGURATION 2.1 Configure PPP 1 (ADSL) This PPP interface should already be configured for use with the ISP. You should confirm that you have a working ADSL connection before proceeding with this configuration. The PPP 1 interface needs to be configured to be “always on”. The inactivity timer should be set to 0.
Click OK 5
2.2 Configure PPP 4 (PSTN) It will be necessary to configure PPP 4 as an outbound interface as the default is for the interface to accept incoming calls. Then ISP configuration will be added. Navigate to the following location: Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 4 > Standard Scroll to the bottom of the page and click “Load dialling defaults”.
Click OK Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 4 > Advanced The PSTN interface needs to be configured so that if PPP 1 (ADSL) is up and in service (i.e. passing data) then this interface is not allowed to initiate a connection.
Click OK 2.3 Configure the Default Routes It is necessary to configure two default routes, one for PPP 1 and one for PPP 4. The PPP 1 default route needs to be set so PPP 4 is deactivated when PPP 1 returns to service after a successful recovery.
Click OK 2.4 Configure the Firewall The firewall should be configured to monitor the ICMP requests generated by PPP 1. If the firewall detects that 3 consecutive ICMP echo requests have failed, it will take PPP 1 out of service and deactivated thus allowing PPP 4 to come up. The IP address in the firewall rule must be the IP address that PPP 1 is sending pings to. The recovery code will then test the ADSL connection before bringing it back into service.
inspect-state – monitor the pings for echo replies and allow them back in oos 10 t=3 c=3 d=3 – if 3 consecutive pings fail, deactivate PPP 1 and start recovery procedures after 10 seconds. This 10 second timer could be increased (by editing the firewall rule) to prevent the Digi Transport from switching rapdily between PPP 1 and PPP 4 in the case where PPP 1 works intermitantly. This “oos 10” can be thought of as a de-bounce timer in the context of this application note.
3 TESTING 3.1 Simulate a failure To test the fail over and recovery you will need to configure the PPP interface to ping a IP address that you can easily stop responding to ICMP requests (either through the use of a firewall or by physically disconnecting it from the network). You will also need to alter the firewall rule so it monitors the same IP address that PPP 1 is pinging.
ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp ppp 4 4 4 4 4 4 4 4 4 4 4 username "user@isp.com" epassword "encrypted" phonenum " 0845 1400101" use_modem 3 aodion 1 pwr_dly 60 autoassert 1 ipsec 1 l1iface "Default" inhibitno "1" inhmode 1 ana ana ana ana ana ana 0 0 0 0 0 0 anon ON l1on ON xoton OFF lapdon 0 lapbon 0 logsize 45 4.2 Digi Transport Firmware Versions This is the firmware \ hardware information: Digi TransPort DR6410-HIA DSL2/2+ Router Ser#:60000 Software Build Ver5081.
PollANS PPPOE BRIDGE MODEM CC (Option 3G) FLASH Write Command Interpreter SSLCLI OSPF BGP QOS RADIUS Client SSH Server SCP CERT LowPrio Tunnel TEMPLOG OK Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: Revision: 1.2 1.0 1.1 1.4 1.2 1.38 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.2 1.
