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Design issue xDSL with cellular (UMTS) backup

Hi all,

I am currently looking for a way to design a solution which incorporates a primary xDSL WAN connection with a cellular interface (UMTS) as backup, over two separate C1841 routers. So one router with xDSL WAN, the other router on cellular WAN.

The solution works fine if implemented on a single C1841 router with a "backup interface cellular 0/1/0" configured on the ATM0 interface.

However, this solution will not work in a situation with two routers.

According to cisco documentation found on this site, there is an option to use a floating static, and/or configuring IP SLA.

However, I would like to keep the cellular interface in a "standby mode" or "shutdown" until I actually need to start using it (when xDSL fails).

The cost for data sent over cellular is quite high, so I want to avoid sending any data over cellular if there is no need to.

Any help would be greatly appreciated !

  • WAN Routing and Switching
Everyone's tags (2)
2 REPLIES
Hall of Fame Super Gold

Re: Design issue xDSL with cellular (UMTS) backup

When configured correctly, the cellular interface will go up only when there is traffic to be sent.

That is the same concept as old ISDN backup.

Recommend you locate an experienced, reputable consultant, or certified cisco partner for the configuration details.

Cisco Employee

Re: Design issue xDSL with cellular (UMTS) backup

You can use the following EEM script in combination with IP SLA and IP:

ip sla 1
   icmp-echo
   timeout 1000
   frequency 3600

ip sla schedule 1 start-time now life forever

track 10 rtr 1 reachability

event manager applet TrackEmergency
    event tag Track_down track 10 state down
    trigger
     correlate event Track_down
    action 1.0 cli command "enable"
    action 1.1 cli command "int cellular0/0/0"
    action 1.2 cli command "no shut"
    action 1.3 wait 15
    action 1.4 puts "Cellular Interface is now up."
    action 1.5 exit

ip route 0.0.0.0 0.0.0.0 Cellular0/0/0 200 (floating static)
ip route 0.0.0.0 0.0.0.0 track 10
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