Configuring 2 T1's to same network with a 3rd "DR" network T1 as "backup"

Posted on 2006-11-27
Last Modified: 2010-04-17
OK Cisco Guru's..Moderatly difficult config help is needed. Scenario:  I have a rather large frame-relay network.  35 sites connecting back to a central Datacenter. Branch sites connect via 2 T1 circuits each (1 ATT, 1 MCI and a single Cisco 2651xm) to T3 ports from each (MCI and ATT) on a single Cisco 7206 at the datacenter. We have now added a DR site with another DS3 and 4k ports at each remote site.  Each site has to connect through the central datacenter to connect to each other and to the internet.  Currently I am doing equal cost load balancing with EIGRP and I wish to keep EIGRP.  I do not want any traffic over the DR network unless all other T1 paths are down. I beleive I can accomplish this by working with the bandwidth and delay statements. Any help would be appreciated.
Question by:dadennis
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
LVL 12

Accepted Solution

pjtemplin earned 100 total points
ID: 18027078
Lie to the router and tell each backup interface that its 'bandwidth N' is perhaps 1/100th of its true bandwidth.  EIGRP should then route away from the backup links.
LVL 28

Assisted Solution

mikebernhardt earned 100 total points
ID: 18029804
There are 2 methods, each have benefits and downsides.

The first is to just modify the bandwidth on the backup links to be less than the primary link. To be safe, also define the bandwidth for the primary link if you haven't already, i.e. 1544 for the primary link and 1000 for the backup link. The up and downside with this method is that if a single route goes away on the primary link, the spokes will use the DR path to get to it if it's available there. You may or may not want this behavior. To get around that, put an outbound distribute list on the hub side (both primary and DR) to all spokes, allowing only the default route out. This also cuts down a LOT on EIGRP queries and calculations. Making the spokes EIGRP stubs will accomplish the same thing.

The other method is to use the backup-interface command on the DR interface. This will keep the interface down until the primary link is physically down, then bring it up. You set timers to manage this. The downside here is that if the link is up but there are no routes, you are lost. The upside is that you never have to worry about traffic going over the DR link when there's another way.

All in all though, the first method is better, and much faster also.

Featured Post

Simple, centralized multimedia control

Watch and learn to see how ATEN provided an easy and effective way for three jointly-owned pubs to control the 60 televisions located across their three venues utilizing the ATEN Control System, Modular Matrix Switch and HDBaseT extenders.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

New Server  was moved from behind Router R2 f0/1 to behind router R1 int f/01 and has now address But we want users still to be able to connected to it by old IP. How to do it ? We can used destination NAT (DNAT).  In DNAT…
Creating an OSPF network that automatically (dynamically) reroutes network traffic over other connections to prevent network downtime.
After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

751 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question