Overview
IP Connectivity is 25% of the CCNA, the single heaviest domain, and where candidates most often pass or fail. It has five deep objectives. Interpreting the routing table covers protocol codes, prefix and mask, next hop, administrative distance, metric and the gateway of last resort. Router forwarding covers how a router chooses a route by longest prefix match, then administrative distance, then metric. Static routing covers configuring and verifying IPv4 and IPv6 static routes, including default, network, host and floating static routes. Single-area OSPFv2 covers neighbor adjacencies, network types, DR and BDR election, and router ID. First hop redundancy covers the purpose and concepts of protocols such as HSRP.
Two objectives, static routing and OSPF, are prime simulation material. The exam rewards reading the routing table, understanding forwarding precedence, and configuring routing correctly, and this domain alone outweighs IP Services and Automation combined.
How it's tested
CCNA questions in this domain are often simulations asking you to configure static routing or OSPF, or to interpret a routing table and forwarding decision. Read routing table entries carefully, applying longest prefix match first, then administrative distance, then metric, before choosing an answer.
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Read the routing table
A routing table is shown, and you interpret codes, administrative distance, metric or the chosen route.
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Configure routing
A connectivity need is described, and you configure static, floating static or OSPF routing.
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Forwarding and redundancy
A forwarding or gateway-redundancy need is described, and you apply the precedence rules or FHRP concept.
A router has learned two routes to the same destination, one via OSPF and one a static route, with different prefix lengths. The router does not simply prefer the lowest administrative distance first: it uses the most specific match. Longest prefix match is applied first, so the route with the longer, more specific prefix is chosen regardless of administrative distance, which is the forwarding rule the exam expects before administrative distance and metric are considered.
Domains 5
Official domains from the Cisco outline, in outline order.
3.1 Interpret the components of a routing tableProtocol codes, prefix, mask, next hop, administrative distance, metric, gateway of last resort.
- What it means
- This covers interpreting a routing table: the protocol codes that show how a route was learned, the prefix and mask, the next hop, administrative distance, metric, and the gateway of last resort for unmatched traffic.
- What to understand
- The routing table shows each known route with a code (such as C for connected, S for static, O for OSPF), its administrative distance and metric in brackets, the next hop, and the gateway of last resort for a default route. Reading this table accurately is foundational to all routing troubleshooting.
- How it shows up
- A routing table is shown, and you must interpret a code, value or the chosen route.
- Common confusion
- Confusing administrative distance with metric, or misreading the protocol codes.
3.2 Determine how a router makes a forwarding decision by defaultLongest prefix match, administrative distance, then metric.
- What it means
- This covers how a router chooses a route by default: first the longest prefix match (most specific route), then, among routes to the same prefix from different sources, the lowest administrative distance, and then the best metric within a protocol.
- What to understand
- Forwarding precedence is a strict order: the most specific matching prefix wins first, regardless of source; only when prefixes are equally specific does administrative distance (trust in the source) decide, and metric breaks ties within a protocol. Understanding this order is essential and frequently tested.
- How it shows up
- Multiple candidate routes are described, and you must determine which the router uses.
- Common confusion
- Applying administrative distance before longest prefix match; the most specific route wins first.
3.3 Configure and verify IPv4 and IPv6 static routingDefault, network, host and floating static routes.
- What it means
- This covers configuring and verifying static routes for IPv4 and IPv6: default routes, network routes, host routes, and floating static routes that act as a backup by using a higher administrative distance.
- What to understand
- Static routes are manually configured with a destination and next hop or exit interface. A default route (0.0.0.0/0) catches unmatched traffic, a host route is a /32 or /128, and a floating static route has a higher administrative distance so it is used only if the primary route fails. Configuring these correctly is core, tested material.
- How it shows up
- A static routing need is described, and you must configure the default, host or floating static route.
- Common confusion
- Misconfiguring a floating static route's administrative distance, or confusing a default with a network route.
3.4 Configure and verify single-area OSPFv2Neighbor adjacencies, network types, DR/BDR, router ID.
- What it means
- This covers configuring and verifying single-area OSPFv2: forming neighbor adjacencies, point-to-point and broadcast network types, designated router and backup designated router election, and the router ID.
- What to understand
- OSPF is a link-state interior gateway protocol. Neighbors must agree on parameters to form adjacencies; on broadcast networks a DR and BDR are elected to reduce adjacencies; and the router ID identifies each router, chosen by highest loopback or configured value. Configuring OSPF and verifying neighbors and routes is prime simulation material.
- How it shows up
- An OSPF need or output is described, and you must configure OSPF or interpret adjacencies and election.
- Common confusion
- Misunderstanding DR/BDR election or why two routers fail to form an OSPF adjacency.
3.5 Describe the purpose, functions, and concepts of first hop redundancy protocolsHSRP and gateway redundancy.
- What it means
- This covers the purpose and concepts of first hop redundancy protocols such as HSRP: providing a redundant default gateway so hosts keep connectivity if one gateway router fails, using a shared virtual IP address.
- What to understand
- First hop redundancy protocols let multiple routers share a virtual gateway IP, so if the active router fails a standby takes over transparently to hosts, which use the virtual IP as their default gateway. Understanding the purpose and basic operation, rather than deep configuration, is what the exam expects here.
- How it shows up
- A gateway-redundancy need is described, and you must identify the first hop redundancy concept.
- Common confusion
- Misunderstanding that hosts point to a virtual IP shared by the redundant routers.
High-yield concepts
The terms, rules and formulas this domain turns into questions most often.
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Routing table codes
C, S, O and others show how a route was learned.
- Remember
- Read codes to understand the table.
- Tested as
- Routing questions.
- Trap
- Misreading the codes.
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Administrative distance
Trustworthiness of a route source.
- Remember
- Lower is preferred.
- Tested as
- Forwarding questions.
- Trap
- Confusing with metric.
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Metric
Cost within a routing protocol.
- Remember
- Breaks ties within a protocol.
- Tested as
- Forwarding questions.
- Trap
- Confusing with administrative distance.
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Longest prefix match
Most specific route wins first.
- Remember
- Applied before administrative distance.
- Tested as
- Forwarding questions.
- Trap
- Applying AD first.
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Default route
0.0.0.0/0 catches unmatched traffic.
- Remember
- The gateway of last resort.
- Tested as
- Static routing questions.
- Trap
- Confusing with a network route.
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Floating static route
Backup route with higher administrative distance.
- Remember
- Used only if the primary fails.
- Tested as
- Static routing questions.
- Trap
- Wrong administrative distance.
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OSPF adjacencies
Neighbors agreeing on parameters.
- Remember
- Required to exchange routes.
- Tested as
- OSPF questions.
- Trap
- Mismatched parameters block adjacency.
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DR and BDR election
Reduce adjacencies on broadcast networks.
- Remember
- Elected by priority then router ID.
- Tested as
- OSPF questions.
- Trap
- Misjudging the election.
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OSPF router ID
Identifies each OSPF router.
- Remember
- Highest loopback or configured.
- Tested as
- OSPF questions.
- Trap
- Misunderstanding router ID selection.
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First hop redundancy
Redundant default gateway via a virtual IP.
- Remember
- Standby takes over on failure.
- Tested as
- FHRP questions.
- Trap
- Hosts not pointing to the virtual IP.
Side by side
Concepts candidates mix up, compared on the point that decides the answer.
Administrative distance vs. metric
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Administrative distance | Trust in the route source | Compares across protocols | Confusing with metric |
| Metric | Cost within a protocol | Breaks ties within one protocol | Confusing with AD |
Forwarding precedence
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Longest prefix match | Most specific route | Applied first | Applying AD first |
| Administrative distance | Lowest preferred | For equally specific routes | Ignoring prefix length |
| Metric | Best cost | Ties within a protocol | Using across protocols |
Static vs. floating static route
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Static route | Manually configured primary | Default administrative distance | Confusing with floating |
| Floating static | Higher administrative distance backup | Used only if primary fails | Wrong AD value |
Exam traps
Each trap is an answer that looks right. Learn the clue that should change your mind.
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AD before prefix match
- What candidates pick
- Choose the route with the lowest administrative distance regardless of prefix length.
- Why it looks right
- Lower AD seems most trusted.
- Why it's wrong
- Longest prefix match is applied first; the most specific route wins before administrative distance is considered.
Clue to watch for Candidate routes have different prefix lengths.
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Metric across protocols
- What candidates pick
- Compare OSPF cost against a static route's metric to choose.
- Why it looks right
- Both have a metric.
- Why it's wrong
- Metric only compares routes within the same protocol; administrative distance compares across protocols.
Clue to watch for The routes come from different protocols.
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Floating route always active
- What candidates pick
- Configure a backup static route with the same administrative distance as the primary.
- Why it looks right
- It is a backup route.
- Why it's wrong
- A floating static route needs a higher administrative distance so it is used only when the primary fails.
Clue to watch for A backup route should only activate on primary failure.
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OSPF adjacency ignores parameters
- What candidates pick
- Expect two routers to form an OSPF adjacency despite mismatched parameters.
- Why it looks right
- Both run OSPF.
- Why it's wrong
- Neighbors must agree on parameters such as area, timers and subnet to form an adjacency.
Clue to watch for Two OSPF routers do not become neighbors.
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Hosts point to a physical gateway
- What candidates pick
- Point hosts to a physical router IP when using first hop redundancy.
- Why it looks right
- The router has an IP.
- Why it's wrong
- With FHRP, hosts use the shared virtual IP so a standby can take over transparently.
Clue to watch for Gateway redundancy must be transparent to hosts.
Answer framework
For any Domain 3 scenario, use these steps to find the answer CCNA expects.
- Read the routing table accurately, identifying codes, administrative distance, metric, next hop and the gateway of last resort.
- Apply forwarding precedence in order: longest prefix match first, then lowest administrative distance for equally specific routes, then best metric within a protocol.
- Configure static routes for IPv4 and IPv6, using default and host routes as needed and a higher administrative distance for floating backup routes.
- Configure single-area OSPFv2, ensuring neighbors agree on parameters, and interpret DR/BDR election and the router ID.
- For gateway redundancy, apply first hop redundancy concepts so hosts use a shared virtual IP with transparent failover. Where two routes seem to fit, pick the one with the longest prefix match, then the lower administrative distance.
Practice question
Want more like this? The CCNA practice test has questions for every domain.
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Study strategy
Give this domain the most study time, because at 25% it is the heaviest and usually decides pass or fail, and it alone outweighs IP Services and Automation combined. Study it in order, since each piece builds on the last. First, master reading the routing table until every code, administrative distance and metric is clear. Then internalize forwarding precedence: longest prefix match first, then administrative distance, then metric, which is a frequent trap.
Next, practice static routing hands-on, including default, host and especially floating static routes with their higher administrative distance. Then invest heavily in single-area OSPFv2, which is prime simulation material: forming adjacencies, DR/BDR election and the router ID. Finally, learn the first hop redundancy concepts.
Because static routing and OSPF appear as simulations, configure them repeatedly in a lab. If practice scores force a choice, fix this domain first. Add a floating static route with a higher administrative distance, shut the primary link, and confirm in the routing table that the backup route takes over. Afterwards, move to Domain 4, IP Services.
FAQ
How much of the CCNA is Domain 3?
IP Connectivity is 25% of the exam, the single heaviest domain, and it alone outweighs IP Services and Automation combined.
What is the difference between administrative distance and metric?
Administrative distance measures how trustworthy a route's source is and compares routes from different protocols, with lower preferred. Metric is the cost within a single protocol and breaks ties among routes from that protocol.
How does a router choose between routes by default?
It applies longest prefix match first, choosing the most specific matching route regardless of source. Only among equally specific routes does it use the lowest administrative distance, then the best metric within a protocol.
What is a floating static route?
A backup static route configured with a higher administrative distance than the primary route, so it is installed and used only when the primary route fails.
Why might two OSPF routers fail to form an adjacency?
Because they disagree on required parameters such as the area, subnet, or timers. OSPF neighbors must match on these to form an adjacency and exchange routes.
What do first hop redundancy protocols do?
They let multiple routers share a virtual gateway IP address so that if the active router fails, a standby takes over transparently, and hosts keep using the same virtual IP as their default gateway.
How does Domain 3 connect to the rest of the exam?
It routes across the switched network from Domain 2 using the addressing from Domain 1, and its routing underpins the services of Domain 4 and the security of Domain 5.
Other Networking certifications
Where the same subject shows up in other exams. Cards marked "Same subject" open the matching domain.
Test your Domain 3 knowledge
You have covered the routing table, forwarding, static routing, OSPF and FHRP. Test whether you can configure and interpret routing under exam conditions.