Routing

Routing Tables and Route Selection

Learn how routers use routing-table entries to decide whether a destination is local, which next hop to use, and how competing routes are handled.

Intermediate12 min read
Routing lessonNetworkingPractice

UNTIMED COACHING

Practice before the pressure

Use feedback to correct the model, not merely memorize an option position.

GUIDED PRACTICE

Practice the lesson questions

Answer normal lesson questions without a timer. Every answer includes an explanation, and incorrect answers can be tried again before continuing.

CONCEPT MODELS

See the lesson as a system

Use these visual guides to connect the key ideas before answering the questions.

From Destination to Forwarding ActionA router matches a destination to forwarding information, then sends the packet directly or toward another router.
From Destination to Forwarding ActionFlow from an IP destination through route matching to direct or forwarded delivery.
IP destinationPacket's intended address
Routing tableAvailable destination matches
Selected entryInterface and next hop
Delivery decisionDirect or forwarded path
Route Types and ReachabilityConnected reach, explicit static paths, and broad defaults provide different ways to forward traffic.
Route Types and ReachabilityPartition showing direct delivery, static forwarding, and default fallback.
Direct deliveryDestination uses local path
Static routeConfigured particular path
Default routeFallback broad path
Remote destinationNeeds another router
Overlapping Routes and Route LifetimeOverlapping prefixes require selecting the most specific applicable range, while unusable forwarding information can remove a route.
Overlapping Routes and Route LifetimeFlow from overlapping entries through specificity and usable forwarding information to an installed route.
Matching entriesSeveral ranges cover destination
SpecificityNarrower range gets priority
Usable forwardingInterface and next hop work
Installed routeAvailable for forwarding