Home Routing BGP Cisco BGP Configuration [Cisco] Shadow connection with BGP

It is a one of fail-over solution. Most ISP has this service. For the shadow link, probably you would pay less than primary connection. Only the primary connection processes traffic in a normal operating state. If the primary connection experiences connectivity issues, all traffic is forwarded over the shadow connection until such time as the primary connection again becomes available.

Testing Environment

  • Same ISP with physically separated two serial connection(T1)
  • Using BGP
  • Two WAN goes into a router


Sample configuration

interface Ethernet0
ip address x.x.x.1 
interface Serial0
description primary link
ip address y.y.y.1   
interface Serial1
description shadow link
ip address z.z.z.1  
router bgp [Customer ASN]
no synchronization
no bgp log-neighbor-changes
network x.x.x.0 mask     
neighbor y.y.y.1 [remote-as Other side ASN 1]
neighbor z.z.z.1 [remote-as Other side ASN 2]
neighbor z.z.z.1 route-map shadow in
neighbor z.z.z.1 route-map shadow out
no auto-summary
route-map shadow permit 10
set metric 10



  • Cisco 2811 Integrated Service Router: 2811 chassis, 64MB Flash (default), 256MB DRAM (default)
  • Two 1-port T1 WAN Interface Cards (WIC-1DSU-T1-V2)
  • Cisco IOS version 12.3.11T2 SP Services

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