Failover options on WAN router?

Andy White · ‎06-18-2010

Hello,

We have a router that is our gateway to one of our WAN's. It is a 1841 router with a serial port using the EIGRP protocol, then fast ethernet just into one of our Cisco 3750 switchs. I want to put some redunancy on this link should the 1841 fail what options do I have?

Ganesh Hariharan · ‎06-18-2010

Hello,

We have a router that is our gateway to one of our WAN's. It is a 1841 router with a serial port using the EIGRP protocol, then fast ethernet just into one of our Cisco 3750 switchs. I want to put some redunancy on this link should the 1841 fail what options do I have?

Hi Andy,

Easy way of configuring a redundacny in failover of links,if primary goes down then secondary will automatically comes up.

Add a higher metric to the default route on the 2nd link

ip route 0.0.0.0 0.0.0.0 (Primary interface)
ip route 0.0.0.0 0.0.0.0 (Secondary interface)

Hope to Help !!

Ganesh.H

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TODD RIEMENSCHNEIDER · ‎06-18-2010

Andy,

Could you explain you existing set up a little more? Redundancy can have its challenges depending on how your environment is set up. I am assuming you want redundant WAN connectivity.

You have one wan connected via a Cisco 1841 connected to 3750.

Is the WAN you reference the Internet or a Corporate WAN?
Who are you peering eigrp with?
How are the WAN routes learned by your core Infrastructure
How is your 3750 connected to the Cisco 1841? Are you doing any routing on it? Is your 3750 simply acting as a Layer 2 switch?
You stated you want failover, where and how is your other WAN connected into your environment relative to this solution?
Are there any Firewalls in play in this environment?

-Todd

Andy White · ‎06-18-2010

The WAN link itself is monitored by our WAN provider but the router is ours and I really mean some sort of hardware redundancy should the 1841 fail?

1.) Corp WAN

2.) Only the WAN

3.) Our gateway router is part of the EIGRP, so our server and PC use this as their gateway.

4.) Just L2

5.) The WAN router just has a serial port our to the WAN and the inside ethernet plugs int othe 3750 vlan.

6.) No, although I will add an access list as somepoint to the WAN router.

TODD RIEMENSCHNEIDER · ‎06-18-2010

Andy,

If this router is your only means to connect to this WAN you have a single point of failure. The only way to survive a hardware failure is with redundant hardware. The easiest thing you could do is get another router with a redundant connection to the wan, you could run a first hop redundancy protocol between the two routers. HSRP is the most common. Set up tracking to monitor your WAN interface. Set up all your PC/Servers with a gateway address of the HSRP address. This would protect you from hardware failure as well as a wan failure.

If I missed something with regard to how the other wan may come into play let me know.

-Todd

Andy White · ‎06-18-2010

Thanks, I can get another router but what will I need for the interfaces? I only have one serial WAN link that goes into the router, how woudl I make this available to the other router should this one fail? I understand the HSRP part as I have confgiured this before, I just am not sure about the physical side.

TODD RIEMENSCHNEIDER · ‎06-18-2010

Unfortunately you would need another serial interface and a redundant wan connection in the solution I am proposing. This solution will provide you dynamic failover in the event of a wan or router failure. You wouldn't have to do anything for it to failover. There is no way for the other router to use the broken routers serial interface if your router dies. If your working with a shoe string budget your other option is to configure a cold standby router. That is a router will have an identical config to your current that will simply be ready to replace the other one in the event of a failure. It wont protect you from a link failure on your wan though.

Andy White · ‎06-18-2010

I guess an option woudl be to do the HSRP and move the serial to the active should it fail?

TODD RIEMENSCHNEIDER · ‎06-18-2010

That is an option. Obviously not the most ideal, but it is what it is. You wouldnt need to track the wan interface with the HSRP config. It would be good from a pure router failure standpoint, because and it would allow you to have it ready and online so all you would need to do is pop the serial connection in and your off to the races. The other thing about having it online is you can keep the configs up-to-date. You would want a serial interface module in the standby router so that you can apply any changes to the wan interface you make. Basically you will have a warm standby.