Solved: Ethernet with ISDN Backup

hclisschennai · ‎03-13-2009

Hi All,

I have a link to my headoffice in ADSL. I am using ADSL Modem having ADSL interface and Ethernet Interface. This Ethernet Interface is connected to Cisco 1841 Router. I want to backup this link using ISDN.

I have configured both Ethernet Interface and ISDN and it is working perfectly.

But ISDN link is not coming up when the primary links is down. Then i found that, even though the ADSL link is down the Ethernet remains up due to ADSL Modem is ON.

How i have to configure my router to dynamically detect the link failure and bring the ISDN up and make the ISDN down once the ADSL (Primary) link is up again

Can you please help me

R.B.Kumar

JamesLuther · ‎03-14-2009

Hi,

ip sla is used with static routing. However if you have EIGRP configured over the ADSL connection then the route will drop out of the routing table when the line goes down.

Are you sure that the route is still staying in the routing table? When the primary link goes down what routing mechanism are you using to bring up the ISDN (EIGRP or floating static?)

If you prefer then please post your configuration.

Regards

View solution in original post

John Blakley · ‎03-13-2009

You might take a look at this link:

http://www.cisco.com/en/US/docs/ios/12_3/12_3x/12_3xe/feature/guide/dbackupx.html#wp1087990

HTH,

John

HTH, John *** Please rate all useful posts ***

hclisschennai · ‎03-14-2009

Hi john,

Thanks for your reference. It is a good document.

But it states the solution for static route only.

How to achieve IP SLA MONITORING in dynamic routing protocols like EIGRP

Can you please help me

R.B.KUMAR

JamesLuther · ‎03-14-2009

Hi,

ip sla is used with static routing. However if you have EIGRP configured over the ADSL connection then the route will drop out of the routing table when the line goes down.

Are you sure that the route is still staying in the routing table? When the primary link goes down what routing mechanism are you using to bring up the ISDN (EIGRP or floating static?)

If you prefer then please post your configuration.

Regards

JamesLuther · ‎03-14-2009

Hi,

I'm guessing that you are currently routing towards the primary via a static route with the interface option?

If you run a routing protocol between the sites then the routing protocol will detect that the link has failed. You can then have a floating static (with a higher admin distance) pointing towards the ISDN interface.

If you decide to configure a routing protocol on the ISDN interface too then ensure that you configure snapshot routing or the OSPF demand circuit feature.

Regards