Cisco 3825 Router – Dual WAN Failover

ciscofailoverrouterrouting

My Cisco 3825, (ISR?) is running fine now, thanks to a lot of help. We've now gotten another WAN link from a different ISP for redundancy.

What I need is to know how to configure the router to be able to Fail Over if the main link has an issue. I don't want to load balance.

  1. Is this possible?
  2. If so, how, e.g. commands/code to implement this

I've seen something called HSRP, but the article seemed to only reference Catalyst devices, so I'm not sure if it's a thing on my router, and also, it seems to deal more with multiple routers, not a single one with two WAN links.

I will also need to purchase another card to add a port for this new connection, could someone tell me exactly what I'd need?

EDIT: added topology per request
Office Network Topology

Best Answer

Couple of things. First, the link may not go down so depending on link down to failover may not actually work. Second is NAT/PAT. Cisco has published a how to for exactly what you are looking to do. See ISP Failover with Default Routes using IP SLA Tracking

Introduction

This document describes how to configure WAN (or ISP) redundancies, wherein multiple WAN links terminate on the same end router. This document also explains how to configure Network Address Translation (NAT) when there are multiple ISP's for internet connectivity and you want seamless failover i.e. when Primary ISP goes down then Secondary takes over with correct NAT with the use of the secondary ISP's public IP address.

enter image description here

Related Topic