Describe a BGP setup with two routers in your organization, each connected to a different ISP via EBGP, and connected to each other via IBGP. What problems can arise in this setup, and how can they be avoided?

Question

Accepted Answer

IBGP setup can lead to unintended transit AS issues; implement route filtering to prevent this.

IBGP routers do not advertise routes learned from one IBGP peer to another, preventing loops.
Without proper configuration, internal routers may inadvertently become transit AS for external traffic.
Use route filtering or prefix lists to control which routes are advertised to prevent transit behavior.
Implementing a route reflector or confederation can help manage IBGP sessions without creating transit paths.
Example: If Router A learns a route from ISP 1 and Router B learns from ISP 2, they shouldn't forward each other's routes.

Asked in Commonwealth Bank of Australia, India

Describe a BGP setup with two routers in your organization, each connected to a different ISP via EBGP, and connected to each other via IBGP. What problems can arise in this setup, and how can they be avoided?

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