Link failover between Gig interface and Serial interface in cisco 3845

[rite2anil]

  Hi All,

I am using cisco 3845 ( Adv. ip services IOS version 15.0(1)M3 as a remote site. I have two ISPs connecting on this router's Gig 0/1 interface as a Primary and  on Serial 0/0/0 interface as a Secondary.my concern is : Traffic should always in/out via Primary ISP ( Gig0/1) and when it goes down then Serial 0/0/0 should be in use. Both links are MPLS links and routing is BGP but at present bgp is configured for primary link only.

Please suggest for the bgp configuration for both neighbors and link failover between Gig0/1 & Serial 0/0/0 interfaces.

Best Regards,

Anil Kumar

[daniel.dib]

Can you run BGP to the secondary one as well? How do you decide between which ISP to use today? For both incoming and outgoing traffic.

You could have a floating static route but that would only take care of outgoing traffic.

Daniel Dib
CCIE #37149

[Mir Navazish Ali]

Hi Anil,

Below is the topology you are looking to do a BGP failover

                  /---------\

              ////           \\\\

             |                   |

            |      Internet       |

             |                   |

              \\\\           ////

                 |\---------||

    192.168.1.6  |          ||192.168.1.2

                 |          ||

      Serial0/0/0|          ||GI0/1

                 |          ||

                 |          ||

     192.168.1.5 |          ||192.168.1.1

              +--+----------++---+

              |                  |

              |   cisco 3845     |

              |                  |

              +------------------+

Below are the possible configurations you can use.

ip prefix-list DEFAULT-IN seq 5 permit 0.0.0.0/0

router bgp

neighbor 192.168.1.2 remote-as

  neighbor 192.168.1.6 remote-as

address-family ipv4

  no synchronization

  neighbor 192.168.1.2 activate

  neighbor 192.168.1.2 route-map IN_PRIMARY in

  neighbor 192.168.1.6 activate

  neighbor 192.168.1.6 route-map IN_SECONDARY in

  neighbor 192.168.1.6 route-map OUT_SECONDARY out

route-map IN_PRIMARY permit 10

match ip address prefix-list DEFAULT-IN

set local-preference 200

route-map IN_SECONDARY permit 10

match ip address prefix-list DEFAULT-IN

set local-preference 90

route-map OUT_SECONDARY permit 10

set as-path prepend 100 100 100 100 100

This is just a basic setup how you could achieve the failover, request you to please test the same before deploying it. I have just visualized a basic scenario and hence the configurations. I am assuming that your ISP will be sending a default route.

I hope this helps.

Thanks

Mir

[rite2anil]

Hi Mir,

I have two ISPs at Remote end and the one connected on Gig interface will always be primary and remains the same for other remote sites and the secondary will be connected on serial interface and remains the same for other sites.

My issue is  at sites end, primary shall be use as an Active and Secondary shall be use as an passive.I think this will work in my case.

Thanks & Regards,

Anil