Why policy matters
When several clouds and sites exchange routes through a router, every route learned from one connection could be passed to all the others. Without policy, you may create paths you never intended — or expose networks that should stay private.
Principle 1: Advertise the minimum
Each connection should receive only the prefixes it needs to reach. A development VPC rarely needs routes to production databases.
Principle 2: Filter what you accept
Define which prefixes each connection is allowed to announce. Reject anything else. This protects you from misconfigurations on the other side.
Principle 3: Choose primary paths explicitly
Where multiple paths exist, use local preference or MED to choose a primary and backup. Do not leave it to tie-breakers.
Principle 4: Control transitive reachability
Decide whether cloud A should reach cloud B through the router. If not, filter accordingly.
Principle 5: Set limits
Maximum-prefix limits on each session prevent a mistake from flooding the router with routes.
Tools
Peer1ix Cloud Router lets you define these policies per connection centrally. Review them whenever you add a cloud or site.
