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Application Note 34
Configuring ADSL to backup to PSTN/ISDN with
automatic testing and recovery back to ADSL.
UK Support
29 December 2009
1
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Contents 1 Introduction ............................................................................................................................................... 2 1.1 Outline ............................................................................................................................................... 2 1.2 Assumptions ...................................................................................................................................... 2 1.3 Correctio
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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 1.1 Re-branded to Digi Transport 3
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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. Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 1 > Standard Parameter Setting Description Always on mode ON Configures interface as always on Inactivity timeout (s): 0
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Click OK 5
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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”. The PPP 4 configuration needs to be configured to be “always on” and have a power up delay of 60 seconds to allow the ADSL c
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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. Parameter Setting Description Inhibit auto-activation when these Inhibit auto-activation of PPP 4 when PPP 1 PPPs are active 1 is active Inhibit if other PPP is Inhibit mode Only inhibit if PPP 1 is passing data active and not OOS 7
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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. Configuration - Routing > Default Route 0 Parameter Setting Description Interface PPP Default route 0 is via PPP 1 Interface # 1 Deactivate interface PPP PPP 4 will be deactivated when this route comes back into service after an outa
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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. When the recovery is suc
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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. r=ping,10,5 rd
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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. Once you have the IP address configured and the Digi Transport router is up on the main WAN link, remove your
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ppp 4 username "user@isp.com" ppp 4 epassword "encrypted" ppp 4 phonenum " 0845 1400101" ppp 4 use_modem 3 ppp 4 aodion 1 ppp 4 pwr_dly 60 ppp 4 autoassert 1 ppp 4 ipsec 1 ppp 4 l1iface "Default" ppp 4 inhibitno "1" ppp 4 inhmode 1 ana 0 anon ON ana 0 l1on ON ana 0 xoton OFF ana 0 lapdon 0 ana 0 lapbon 0 ana 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
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PollANS Revision: 1.2 PPPOE Revision: 1.0 BRIDGE Revision: 1.1 MODEM CC (Option 3G) Revision: 1.4 FLASH Write Revision: 1.2 Command Interpreter Revision: 1.38 SSLCLI Revision: 1.0 OSPF Revision: 1.0 BGP Revision: 1.0 QOS Revision: 1.0 RADIUS Client Revision: 1.0 SSH Server Revision: 1.0 SCP
