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Backup Route Scenarios using different paths Part 1

We have four contract sites that are we are using a combination of Frame Relay, Point-to-Point T1, Wireless and ISDN connectivity.

Primary connection from Contract sites 1336 and 1291 back to our Home Office in Jacksonville are via 512K Frame Relay. We use a Cisco wireless bridge to connect Contracts 1291 and 1326 to one another and the same scenario is used between contracts 1336 and 1311. A point-to-point T1 circuit is connected between contracts 1326 and 1336 and each site has an ISDN backup.

Contracts 1291, 1326 and 1336 have a Cisco 2811 Primary Router and Cisco 1841 ISDN backup router. Contract 1311 has a 2611XM and a Cisco 802 ISDN backup router.

We are running HSRP between the Primary routers and ISDN backup routers. My goal is this, if a Frame Relay circuit fails at either 1291 or 1336 I want traffic from those sites to be able to use the point-to-point T1 connection as the first backup and then rely on the ISDN as a tertiary backup. Granted the wireless links are considered to be up in this scenario. If the Wireless were to fail between 1291 and 1326 then I would want contract 1326 to utilize the point-to-point T1 until wireless connectivity restored. From 1291’s perspective if the frame fails it would have to traverse the wireless to hit the point-to-point and in the event of a loss of wireless or T1 then the site would rely on its ISDN backup. I am thinking that a combination of weighted routing and some tracking of either IP routes or specific interfaces. Any one have any ideas? One other caveat is that in our last test of this when we simulated a failover to ISDN once the primary link was restored the ISDN refused to go down and caused some routing loop issues.

Each site has multiple subnets and each site has is using BGP. We will be using EIGRP between the wireless segments to pass routing information so that it knows how to get back to our main office. I have attached the preliminary configs for the routers as well as a diagram to give an idea of what we are trying to accomplish. Any ideas would be appreciated.


Part 2 with more configs and a drawing to follow


Re: Backup Route Scenarios using different paths Part 1

This is a lot of config, to be done.I can give you a few suggestions.

a. Enable a routing protocol such as EIGRP or OSPF.

b. Configure ISDN links not to get triggered by EIGRP or OSPF hellos (Use a dialer list and deny eigrp or ospf packets from triggering the link or use ospf demand circuit)

c. Use frame-relay end to end keepalive so that you can detect PVC failure on the FR cloud.

d. Configure HSRP with higher priority on frame router at sites 1336 and 1291 to help prefer the frame link and use HSRP tracking feature to monitor interface failure (Frame sub interface failure). Once this interface fails, HSRP will kick in the standby router, which has ISDN and wireless interface.

e. Order of preference of interfaces can be tweaked by adjusting EIGRP or OSPF costs on interfaces. (Delay for EIGRp and bandwidth for OSPF)

Configure EIGRP or OSPF cost (least value) on the Frame interface, (second least value) on the Wireless bridge (ethernet interface) and highest value on the ISDn interface.

Rest should work automatic.