Setting up back-up for Internet Connection through T1 line.

Mar 16, 2006 3 Replies
C

Hello all. I want to find out if it is feasible and possble to set up a backup connection to the Internet going through the T1 line between two offices and through the other ISP connection.



This is my Network diagram :



ISP1 --------Office 1 || || || || ISP2---------Office 2


---- : Fast Ethernet connection to ISP || : Frame Relay T1


I want to set it up so that if Office 1 loses Internet Connectivity the traffic can go through the T1 to the Office 2 and then out to the Internet.



I have Cisco 1721 and 3620 routers connecting the two offices. And Cisco PIX-515e's going to the Internet. I am running EIGRP on the T1.



I can try a load balancer like a Radware Link-Proof, but I am not sure that it will do the job.



Any suggestions are welcome.


Thank you in advance



Dmitry.



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M

  1. Step 1 - Assuming that default is configured on each router, then on the router for office 2 redistribute static into the EIGRP routing process. This will provide backup given that the link from office 1 to ISP1 fails. Please note there are scenarios where you can loss Internet connectivity without the link to ISP 1 failing. An example would be if the ISP's POP (point of presence) becomes isolated from the rest of the ISP network. Your link remains up but you cannot reach sites on the Internet.
  2. Step 2 - Evaluate implementing Cisco's Reliable Static Routing Backup Using Object Tracking feature. see
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A

Assuming that your company doesn't have its own AS (and is not running BGP with ISP1/ISP2), you'll need to configure address translation in Office 1 for IP netblock used at Office 2, and vice versa. Otherwise ISP1 will drop all packets arriving from Office 1 and having ISP2-provided source IP addresses.

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