Posted by This method will monitor a connection via ICMPWikipedia: The Internet Control Message Protocol (ICMP) is a supporting protocol[2] in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational inform... ping and, on failure, it will bring up the ADSLWikipedia: Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than... line. Below is my setup – you may need to tailor this guide to yours. This method is useful if both connections cannot be up at the same time (possibly because they share an IP address).
- Dialer0 is a PPPoE dialer to a VDSL modem via fa0/0
- Dialer1 is a PPPoATM dialer of ADSL via ATM0/1/0
- The IP I am pinging to detect failure is 83.218.143.225
- The ATM0/1/0 interface is shutdown when not in use
First we’ll add a Track and IP SLA to monitor our primary connection (Dialer0) by pinging our monitor IP (83.218.143.225). This track configuration delays actioning a failure for 10 seconds and a restore by 60 seconds. This is to prevent flip-flopping on the lines:
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track 1 rtr 123 reachability delay down 10 up 60 ip sla 123 icmp-echo 83.218.143.225 source-interface Dialer0 timeout 2000 frequency 4 ip sla schedule 123 life forever start-time now
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Next we’ll add default routes for Dialer0 (linked to Track1) and Dialer1 (with a higher metric). If you already have default routes, remove these first:
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ip route 0.0.0.0 0.0.0.0 Dialer0 track 1 ip route 0.0.0.0 0.0.0.0 Dialer1 254
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Finally we’ll use EEMWikipedia: Cisco Embedded Event Manager (EEM) is a feature included in Cisco's IOS operating system (and some other Cisco OSes such as IOS-XR, IOS-XE, and NX-OS) that allow programmability and automation capabi... applets to monitor track 1 and bring up the ATM interface on failure (and visa versa). This also e-mails us about the event:
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event manager applet TRACK-1-TIMEOUT event track 1 state down action 1.0 cli command "enable" action 2.0 cli command "config terminal" action 3.0 cli command "interface atm0/1/0" action 4.0 cli command "no shutdown" action 5.0 mail server "55.33.44.22" to "to@mail.com" from "from@mail.com" subject "IP SLA 123 Timeout" body "Timeout on primary line" event manager applet TRACK-1-OK event track 1 state up action 1.0 cli command "enable" action 2.0 cli command "config terminal" action 3.0 cli command "interface atm0/1/0" action 4.0 cli command "shutdown" action 5.0 mail server "55.33.44.22" to "to@mail.com" from "from@mail.com" subject "IP SLA 123 Restored" body "Primary line restored"
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You should replace 55.33.44.22 with a valid SMTP server that this router has access to send through and change to@mail.com/from@mail.com to the to/from e-mail addresses respectively.
A full example config (with some bits redacted) can be found here.