Interactive Network Lab · Chapter 01

Routing Protocol
Foundations

Build NovaTech Solutions' network from a single office into a resilient three-site environment. Inspect how routers learn routes, choose paths, and recover from failure.

NovaTech rolloutPhase 1 of 4Role: Junior Network Engineer

Case study: a network built from scratch

LAN AHQ Users10.10.10.0/24

R1HQ Router10.0.12.1

R2Branch Router10.0.12.2

LAN BBranch Users10.20.0.0/16

R3Backup Router10.0.13.3

Core vocabulary · tap to flip

What the router needs to know

Routing table

Inspect R1

Route entries identify a destination prefix, next hop or exit interface, and the source that taught the route.

Source	Destination	Next hop	AD / metric	Status

Selection order

Four filters, in order

1 Prefix length→2 AD→3 Metric→4 ECMP

A later test is used only when the earlier test does not produce a single winner.

Interactive route decision

Route Selection Workbench

Choose a destination and route sources. The workbench applies the router's selection logic.

Destination IPRoute A sourceRoute B source

Candidate	Prefix	Source	AD	Metric

Administrative distance

Local source trust

Lower is preferred only when sources advertise the same prefix. AD is local; it does not travel with the packet.

Failure simulation

Convergence in action

At Phase 4, NovaTech has a backup path. Break the primary R1–R2 link and watch routing move from an unstable period toward a new stable state.

Status: Stable — routers agree on the current best paths.

Static-only routing would require an administrator or a preconfigured floating static route. A dynamic protocol exchanges reachability and recalculates automatically.

Knowledge check

Make the routing decision

R1 learns 10.20.0.0/16 through OSPF (AD 110, metric 30) and RIP (AD 120, metric 2). Which route wins?