IP Connectivity is the largest current CCNA domain. The core skill is to predict the next hop from the routing table, then prove whether the control plane and forwarding path agree.
What to know and how to practise it
Routing-table interpretation and forwarding decisions
Read route source, prefix, administrative distance, metric, next hop, outgoing interface, and gateway of last resort. Apply longest-prefix match first; administrative distance and metric select among competing routes to the same prefix rather than overriding a more specific route.
IPv4 and IPv6 static routes
Configure default, network, host, and floating static routes with the correct next hop or interface. Understand why multiaccess Ethernet routes normally need an appropriate next-hop address and how a higher administrative distance creates backup behavior.
Single-area OSPFv2
Establish adjacencies with correct addressing, area, timers, network type, passive-interface behavior, and unique router IDs. Understand DR and BDR elections on multiaccess networks and advertise a default route only when the design calls for it.
First-hop redundancy concepts
Understand how a virtual gateway improves endpoint default-gateway availability and how active/standby or active/active roles differ conceptually among common first-hop redundancy protocols. Focus on the forwarding outcome and failure behavior required by the blueprint.
Example route-selection proof
A router knows a default route, an OSPF /16, and a static /24 covering the same destination. The /24 wins because it is the longest match. Administrative distance would matter only if two candidate routes described the same prefix length and destination network.
show ip route
show ipv6 route
show ip ospf neighbor
show ip ospf interface brief
show ip protocolsReadiness checklist
- Explain every field of a representative routing-table entry.
- Apply longest-prefix match before administrative distance and metric.
- Configure and verify default, host, floating, IPv4, and IPv6 static routes.
- Troubleshoot an OSPF adjacency in a fixed order.
- Explain first-hop redundancy from the endpoint perspective.
Common mistakes to remove
- Choosing the lowest administrative distance before comparing prefix length.
- Equating a FULL OSPF neighbor with correct route advertisement.
- Adding default-information originate without confirming the required default-route behavior.