BGP Convergence Test (Link failure scenario)

Routing & Switching BGP
1

Hi All,

Need some help to Explain the BGP Convergence Test (Link Failure Scenario) with cisco xRV configuration.
My scenario is i have 3 routers and connected R1 to R2 and R1 to R3, If R1 to R2 link goes down the traffic has to go R1 to R3 Link. Please explain with BGP Configuration with Cisco xRV configuration.

Thanks,
Venkat.

2

Hello Venkat

There are various methods and features that can be used to have BGP deliver failover capabilities. One of the simplest approaches, regardless of the Cisco platform you are using, is to do the following:

This simplified configuration assumes that each router is in a different AS.

For R1, the configuration would look something like this:

router bgp 100
 bgp log-neighbor-changes
 neighbor 10.0.0.2 remote-as 200
 neighbor 10.0.0.3 remote-as 300
 network 192.168.1.0

For R2:

router bgp 200
 bgp log-neighbor-changes
 neighbor 10.0.0.1 remote-as 100
 network 192.168.2.0

And for R3:

router bgp 300

bgp log-neighbor-changes
 neighbor 10.0.0.1 remote-as 100
 network 192.168.3.0

In this example, the 192.168.x.0 network represents the networks behind each router. The 10.0.0.x addresses are the interfaces on the routers that connect them together.

When the link between R1 and R2 goes down, BGP will automatically re-converge and send the traffic to R3. This is because BGP will realize that the path to R2 is unavailable and will choose the next available path, which is through R3.

Keep in mind that this is a very simplified example and actual implementation may require additional configuration depending on your network setup. Additional mechanisms that are involved in such an approach include:

Take a look at the above, and if you have further questions, let us know!

I hope this has been helpful!

Laz