Which rule does a router apply first when selecting a route for a destination packet?

KKey Concepts to Remember

• A Cisco router selects the route with the longest prefix match as the first step in forwarding a destination packet.
• The longest prefix match means the route with the most specific subnet mask that matches the destination IP address is preferred.
• Administrative distance and metrics are only compared when multiple routes have the same prefix length in the routing table.
• Default routes with prefix 0.0.0.0/0 are used only if no more specific route matches the destination IP address.
• Metrics represent route cost within a routing protocol but do not override the longest prefix match rule.
• A router does not consider the age of a route when initially selecting the best route for a packet.
• Longest prefix match ensures subnet-specific routes take precedence over broader network routes in Cisco routing.
• Misunderstanding the order of route selection rules can lead to incorrect assumptions about routing behavior in Cisco devices.