Simple definition
Policy-based routing selects packet forwarding paths using rules such as source address or service rather than destination alone.
Purpose and use
PBR, Policy-Based Routing, selects forwarding behavior using criteria beyond the destination IP address, such as the source address.
How does it work?
Ordered rules match packets and can select a next hop or a separate routing table according to device capabilities.
Example and verification
Validate a rule from the relevant source and inspect its counters and the reachability of the chosen next hop.
Points to watch
The return path can become asymmetric and disrupt a stateful firewall. Overly broad rules can also divert unintended traffic.
In short
PBR changes path selection; it does not replace required routes or security authorization.