Routing Interview Questions and Answers
Routing questions test how a router chooses paths — administrative distance, metrics, longest-prefix match. Get these right and you demonstrate you understand the routing table, not just how to read it. Build the foundation with our routing guide.
How to prepare
Routing interviews centre on route selection order: longest-prefix match first, then administrative distance (which source to trust), then metric (best path within a protocol). Know the default ADs cold and be able to explain why a static route beats OSPF. Practise the logic on our tests.
Frequently asked questions
What is administrative distance?
A router's trust ranking of route sources — lower is more trusted. Connected 0, static 1, eBGP 20, EIGRP 90, OSPF 110, RIP 120, iBGP 200.
If a router learns the same network via OSPF and a static route, which wins?
The static route — AD 1 beats OSPF's 110. Lower administrative distance always wins regardless of metric.
What is longest prefix match?
When multiple routes match a destination, the router uses the most specific one (longest mask). A /24 is chosen over a /16 for an address both contain.
What is the difference between administrative distance and metric?
AD chooses between different route sources (protocols); metric chooses the best path within a single protocol. AD is compared first.
What is a default route?
0.0.0.0/0 — it matches any destination not otherwise in the table, typically pointing toward the internet or a next hop of last resort.
What is a floating static route?
A static route with a deliberately raised AD, so it stays out of the table until the preferred (lower-AD) route fails, then becomes the backup.
What does the router do if no route matches a packet?
It drops the packet and (usually) sends an ICMP destination-unreachable — unless a default route exists to catch it.
What is the difference between static and dynamic routing?
Static routes are manually configured and don't adapt to failures; dynamic protocols (OSPF, EIGRP, BGP) learn and reroute automatically.
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