BGP uses Access Control Lists (ACLs) to filter incoming and outgoing routing updates between BGP peers. These ACLs can be configured to permit or deny specific routes or prefixes between peers, thereby preventing unauthorized or malicious routing information from entering or leaving a network.
ACL filtering is particularly important in BGP because routing information is not authenticated by default, and BGP peers share information with each other based on trust. Without proper ACL filtering, a malicious actor could potentially introduce false or malicious routing information into a network, leading to traffic being redirected to unintended destinations or even causing network outages.
By configuring ACLs to filter BGP updates, network administrators can limit the scope of BGP routing information to only what is necessary for the network to function, preventing unauthorized access and ensuring the integrity of the network.
