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CCNA · Domain 3

IP Routing practice questions

IP Routing is worth 20% of the CCNA exam — the 3rd-heaviest of the 5 domains. Reading the routing table, IPv4 and IPv6 static routes, single-area OSPFv2 and OSPFv3, and first hop redundancy. Official weighting 20%. 6 fully worked examples are further down this page, answers included.

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20%
the 3rd-heaviest of the 5 domains
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190
across 4 topics
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6 sample IP Routing questions, fully explained

Questions from the CCNA bank mapped to domain 3, with the answer key and the reasoning behind every option. None of them repeat the examples on the main CCNA practice page.

Question 1IP Routing

Router R2 has IPv6 unicast routing enabled. Its upstream router uses the global address 2001:db8:acad:12::1 on the link they share. R2 needs an IPv6 route that matches any destination it has no more specific route for. Which command creates it?

Choose one.

  • a
    ipv6 route ::/128 2001:db8:acad:12::1

    ::/128 matches only the unspecified address ::, so it is a host route, not a default route.

  • b
    ipv6 route 2000::/3 2001:db8:acad:12::1

    2000::/3 covers global unicast space only. It is a network route, and destinations outside it would not match.

  • c
    ip route ::/0 2001:db8:acad:12::1

    The ip route command takes IPv4 prefixes and masks. IPv6 static routes use the ipv6 route command.

  • d
    ipv6 route ::/0 2001:db8:acad:12::1 Correct

    ::/0 is the IPv6 default prefix: a zero-length prefix that matches every IPv6 destination.

The concept

An IPv6 default route is a static route to ::/0.

Why that’s the answer

IPv6 static routes use ipv6 route followed by the prefix in slash notation and the next hop. The zero-length prefix ::/0 matches every destination, which makes it the default route. ::/128 is a single-address host route, 2000::/3 is a large network route, and ip route only accepts IPv4.

How to reason it out
  1. Choose the ipv6 route command for an IPv6 route.
  2. Use the zero-length prefix ::/0 for a default route.
  3. Give the upstream router's address as the next hop.

Exam tip: IPv6 default route = ipv6 route ::/0 <next hop>.

CCNA Static Routing: Default, Network, Host and Floating Static Routes (IPv4 and IPv6) — the lesson that teaches this.

Question 2IP Routing

R3 connects to R4 on GigabitEthernet0/0/1. R3's link-local address on that interface is fe80::1 and R4's is fe80::2. An engineer tries to route 2001:db8:20::/64 through R4:R3(config)# ipv6 route 2001:db8:20::/64 fe80::2 % Interface has to be specified for a link-local nexthopWhich command installs a working route through R4?

Choose one.

  • a
    ipv6 route 2001:db8:20::/64 GigabitEthernet0/0/1 fe80::2 Correct

    A link-local next hop is only unique on one link, so IOS needs the exit interface plus R4's link-local address.

  • b
    ipv6 route 2001:db8:20::/64 GigabitEthernet0/0/1 fe80::1

    fe80::1 is R3's own link-local address on that interface, so the next hop points back at R3 rather than at R4.

  • c
    ipv6 route 2001:db8:20::/64 GigabitEthernet0/0/1 2001:db8:20::1

    2001:db8:20::1 is an address inside the destination prefix, not R4's address on the shared link, so neighbor discovery on Gi0/0/1 never resolves it.

  • d
    ipv6 route 2001:db8:20::/64 fe80::2 GigabitEthernet0/0/1

    The parts are in the wrong order. IOS expects the interface first and then the link-local next hop, so this line is rejected as invalid input.

The concept

IPv6 static routes with a link-local next hop need the exit interface.

Why that’s the answer

Every IPv6 interface has a link-local address, and the same fe80:: address can exist on many links. IOS therefore refuses a link-local next hop unless the exit interface is also given, written as the interface first and then the neighbor's link-local address. The other options use R3's own link-local address, a next hop inside the remote prefix that is not on the link, or the right parts in the wrong order.

How to reason it out
  1. Read the error: the route is missing an interface.
  2. Identify the link to R4 (Gi0/0/1) and R4's link-local address (fe80::2), not R3's own fe80::1.
  3. Write the interface first, then the next hop.
  4. Reject a next hop that is not on the shared link.

Exam tip: Link-local next hop? Name the exit interface too.

CCNA Static Routing: Default, Network, Host and Floating Static Routes (IPv4 and IPv6) — the lesson that teaches this.

Question 3IP Routing

R1 reaches 172.16.50.0/24 through R2. The security team wants only traffic to one server, 172.16.50.10, to go through a firewall router whose address is 10.0.15.5. Traffic to the rest of 172.16.50.0/24 must keep using R2. Which static route meets the requirement?

Choose one.

  • a
    ip route 172.16.50.10 255.255.255.0 10.0.15.5

    IOS rejects this with an inconsistent address and mask error, because 172.16.50.10 has host bits set for a /24 mask.

  • b
    ip route 172.16.50.10 255.255.255.255 10.0.15.5 Correct

    A /32 mask matches one address. Longest-prefix match sends only 172.16.50.10 to the firewall router and leaves the /24 route in place.

  • c
    ip route 172.16.50.0 255.255.255.0 10.0.15.5

    This network route covers the whole /24 and moves every host to the firewall path, breaking the second requirement.

  • d
    ip route 172.16.50.10 0.0.0.0 10.0.15.5

    0.0.0.0 here is a /0 mask. IOS rejects 172.16.50.10 with that mask, and a valid /0 route would be a default route, not a single-host route.

The concept

A host route uses a /32 (IPv4) or /128 (IPv6) prefix.

Why that’s the answer

A host route matches exactly one address: mask 255.255.255.255 for IPv4. Because routers forward on the longest matching prefix, the /32 is used for 172.16.50.10 while every other host in the /24 still matches the existing route via R2. A /24 network route would move the whole subnet, and a /24 or /0 mask with a host address is rejected as inconsistent.

How to reason it out
  1. One destination address means a host route.
  2. Use mask 255.255.255.255 for an IPv4 host route.
  3. Rely on longest-prefix match to leave the /24 route working for everyone else.

Exam tip: Host route = /32 (IPv4) or /128 (IPv6); it beats any shorter route.

CCNA Static Routing: Default, Network, Host and Floating Static Routes (IPv4 and IPv6) — the lesson that teaches this.

Question 4IP Routing

Users on R1's LAN can reach every host in 10.10.20.0/24 except the server 10.10.20.99. That server moved from behind R4 to the same LAN as the other hosts behind R3 last week. The engineer checks R1:R1# show ip route static 10.0.0.0/8 is variably subnetted, 6 subnets, 3 masks S 10.10.0.0/16 [1/0] via 10.0.12.2 S 10.10.20.0/24 [1/0] via 10.0.13.3 S 10.10.20.99/32 [1/0] via 10.0.14.4Which change restores reachability to the server without affecting other traffic?

Choose one.

  • a
    no ip route 10.10.20.99 255.255.255.255 10.0.14.4 Correct

    The leftover /32 still sends the server's traffic to R4. Removing it lets 10.10.20.99 match the /24 via R3 like the other hosts.

  • b
    no ip route 10.10.20.0 255.255.255.0 10.0.13.3

    Removing the /24 sends the rest of 10.10.20.0/24 to R2 through the /16 and leaves the stale /32 in place.

  • c
    ip route 10.10.20.99 255.255.255.255 10.0.13.3 5

    With administrative distance 5 this route loses to the existing /32 with distance 1, so it is not installed and nothing changes.

  • d
    ip route 10.10.20.0 255.255.255.0 10.0.14.4 5

    A second /24 via R4 with distance 5 is not installed while the distance-1 route exists, and it would point at the wrong router anyway.

The concept

A stale host route overrides network routes for its one address.

Why that’s the answer

Longest-prefix match picks the /32 for 10.10.20.99 before the /24 or /16 is considered, so the old host route via R4 keeps sending the server's traffic to a router that no longer has it. Deleting the /32 lets the address fall back to the /24 via R3. Adding another /32 or /24 with a higher distance does not help, because distance only chooses between routes to the same prefix and the existing ones have distance 1.

How to reason it out
  1. Notice that only one address fails, which points to a host route.
  2. Find the /32 for 10.10.20.99 and its next hop, R4.
  3. Compare with the server's new location behind R3.
  4. Remove the stale /32 so the /24 applies.

Exam tip: When one host fails and its neighbours work, look for a stale /32.

CCNA Static Routing: Default, Network, Host and Floating Static Routes (IPv4 and IPv6) — the lesson that teaches this.

Question 5IP Routing

R1 learns its default route from OSPF:O*E2 0.0.0.0/0 [110/1] via 10.0.1.1, 2d03h, GigabitEthernet0/0/0The team adds an LTE router at 192.0.2.1 as a backup. The LTE path must carry traffic only when the OSPF-learned default route disappears. Which command meets the requirement?

Choose one.

  • a
    ip route 0.0.0.0 0.0.0.0 192.0.2.1

    Without a distance the static uses 1, which beats OSPF's 110. All internet traffic would move to LTE at once.

  • b
    ip route 0.0.0.0 0.0.0.0 192.0.2.1 120 Correct

    Distance 120 is higher than OSPF's 110, so the static stays out of the routing table until the OSPF default is withdrawn.

  • c
    ip route 0.0.0.0 0.0.0.0 192.0.2.1 100

    100 is still lower than OSPF's 110, so this static would replace the OSPF default rather than back it up.

  • d
    ip route 0.0.0.0 0.0.0.0 192.0.2.1 255

    Distance 255 means the route is never trusted or installed, so the backup would not take over when OSPF fails.

The concept

A floating static route has an administrative distance higher than the route it backs up.

Why that’s the answer

When two sources offer the same prefix, the router installs the one with the lower administrative distance. OSPF uses 110, so a backup static needs a distance between 111 and 254. It then floats: it stays out of the table while OSPF's default exists and is installed as soon as that route is withdrawn. Distance 1 or 100 would take over at once, and 255 means unreachable, so it is never installed.

How to reason it out
  1. Read the primary route's distance from the brackets: 110.
  2. Give the static a distance above 110.
  3. Keep it below 255, which is never installed.

Exam tip: Floating static: distance above the primary's, below 255.

CCNA Static Routing: Default, Network, Host and Floating Static Routes (IPv4 and IPv6) — the lesson that teaches this.

Question 6IP Routing

R1 has two internet links. GigabitEthernet0/0/0 reaches ISP-A's router, 198.51.100.1, via the provider's on-site switch; GigabitEthernet0/0/1 reaches ISP-B's router, 203.0.113.1:ip route 0.0.0.0 0.0.0.0 198.51.100.1 ip route 0.0.0.0 0.0.0.0 203.0.113.1 10ISP-A's router failed an hour ago. GigabitEthernet0/0/0 remains up/up, internet access is down, and show ip route continues to list the default via 198.51.100.1. What explains this?

Choose one.

  • a
    The first route stays installed because its next hop resolves via the up/up subnet on Gi0/0/0 Correct

    A static route with a next hop stays in the table while that next hop is reachable through an up interface. R1 cannot see that the router beyond the provider switch has failed.

  • b
    The second route's distance of 10 is too low to float; a backup needs a distance above 110

    110 matters only when the primary is learned through OSPF. Here the primary is a static with distance 1, so any value from 2 to 254 floats correctly.

  • c
    The second route is ignored because IOS keeps one default route per table and drops the others

    Two default routes can coexist. With equal distances both would be installed and load-shared; with different distances the higher one waits.

  • d
    The first route stays installed because a static route leaves the table when it is deleted from the configuration

    Static routes are also removed when their next hop becomes unresolvable, for example when the exit interface goes down. The issue is that the interface never went down.

The concept

A floating static takes over only when the primary route leaves the routing table.

Why that’s the answer

R1 resolves next hop 198.51.100.1 through the connected subnet on Gi0/0/0. Because the provider switch keeps that interface up/up, the connected route and therefore the primary static stay installed, and the distance-10 backup never floats in. The backup's distance is fine: it only has to be above 1. A static route does leave the table when its next hop becomes unresolvable, which is why the same design fails over correctly when the interface itself goes down. Detecting a failure beyond the local link needs reachability tracking, which plain static routes do not do.

How to reason it out
  1. Confirm the backup's distance (10) is higher than the primary's (1).
  2. Check whether the primary has left the routing table: it has not.
  3. Ask why: its next hop still resolves through an up/up connected interface.
  4. Conclude that a failure beyond the local link is invisible to a plain static route.

Exam tip: A floating static only takes over when the primary route is removed, and a remote failure on Ethernet does not remove it.

CCNA Static Routing: Default, Network, Host and Floating Static Routes (IPv4 and IPv6) — the lesson that teaches this.

What CCNA domain 3 tests, topic by topic

The official exam guide breaks IP Routing into 4 topics. The question bank follows the same split, so a weak topic shows up as a cluster of misses you can go back and read.

Published CCNA practice questions per topic in IP Routing
TopicWhat it coversQuestions
Interpreting the routing tableOfficial CCNA v2.0 exam topic 3.1: Interpret a routing table to identify the next hop for a packet (routing protocol, prefix/mask, administrative distance, metric, and default route).46
IPv4 and IPv6 static routingOfficial CCNA v2.0 exam topic 3.2: Troubleshoot IPv4 and IPv6 static routing — default route; network route; host route; floating static.48
Single-area OSPFv2 and OSPFv3Official CCNA v2.0 exam topic 3.3: Configure single area OSPFv2 for IPv4 and OSPFv3 for IPv6 — neighbor adjacencies (excluding authentication); point-to-point; broadcast (DR/BDR selection); router ID.48
First hop redundancy: HSRP and VRRPOfficial CCNA v2.0 exam topic 3.4: Interpret the operational status of First Hop Redundancy Protocols (HSRP and VRRP).48
Total190

Revise IP Routing before you drill it

CCNA Routing Table: Next Hop, Longest Match and Administrative DistanceMost questions in this topic are evidence-first: the stem shows show ip route, show ip route <address> or show ipv6 route output and asks which next hop and interface a packet uses, which packets are dropped or take the default route, what a code, bracket value or heading line means, or how the table changes after a new route arrives or an existing one is withdrawn. Overlapping prefixes with non-octet masks (and IPv6 /56 or /128 boundaries) test longest prefix match, while scenarios with the same prefix from several sources test administrative distance, including external EIGRP and floating static routes. Some items ask you to judge a stated explanation, such as an AI assistant's analysis, so check both the conclusion and the reasoning against the selection order.CCNA Static Routing: Default, Network, Host and Floating Static Routes (IPv4 and IPv6)Questions in this topic are mostly troubleshooting scenarios with evidence in the stem: a running-configuration line, an IOS error message, show ip route static or show ipv6 route static output, show ip arp entries or a traceroute. You are asked which command meets a requirement, why a route is missing or misbehaving, which configuration line produced an entry, or which next hop a router uses after an interface fails. Read the requirement closely, because a stated limit on scope (which traffic, which prefixes or which devices may change) usually rules out options that would otherwise work. Expect mask and prefix-length precision (network address versus host bits, summaries in IPv4 and IPv6), default-route look-alikes, distance choices for floating routes against static or OSPF primaries, longest match overriding distance, next-hop resolution and recursive dependency, Ethernet failure behaviour, return paths, link-local next hops, ipv6 unicast-routing symptoms, and Select TWO items that ask for every valid form of a route.CCNA Single-Area OSPFv2 and OSPFv3: Adjacencies, DR/BDR, Point-to-Point and Router IDMost questions in this topic are scenario and evidence-first: the stem shows show ip ospf neighbor, show ip ospf interface, show interfaces, show ipv6 route or an ACL and asks what the output means, why an adjacency is missing or stuck, or which single change fixes it. Expect wildcard arithmetic to choose a network statement that matches exactly the required interfaces, router ID prediction from interface tables (including loopbacks that are down and the sticky ID after a change), DR/BDR outcomes from priority and router ID tables including what happens after a DR reloads, and the point-to-point network type read from neighbor output. Stated constraints in the scenario often decide between options that would each work in isolation, and Select TWO items ask for two independent fixes or two true statements. OSPFv3 items focus on its configuration commands, link-local behaviour and router ID. Path selection and administrative distance belong to the routing-table topic, and authentication is not tested here.CCNA First Hop Redundancy: Reading HSRP and VRRP Status, Election, Preemption and FailoverMost questions in this topic are evidence-first: the stem shows show standby brief, show standby, show vrrp output, a running-config excerpt, a host's ARP table or traceroute, or a packet capture, and asks which router forwards, what a state means, why a router is not Active, or what caused a fault. Expect elections decided by priority and then IP address (including three-router groups with a Listen router and the VRRP address owner), preemption scenarios where HSRP and VRRP defaults differ, tracking arithmetic with current versus configured priority, virtual MAC and hello-address conversions between hex group numbers, failover timing and gratuitous ARP behaviour, dual Active/Master troubleshooting, load sharing across groups, and IPv6 gateways learned from router advertisements. Constraints such as a single change, a router you may not touch, or failover that must not get slower decide between workable options, and Select TWO items ask for two true results or two independent causes. Routing-table reading, static routes and OSPF belong to the sibling topics.

Other CCNA domains

Domain 1: Network Infrastructure and Connectivity25% of the exam · 239 questionsDomain 2: Switching and Network Access25% of the exam · 240 questionsDomain 4: Network Services and Security20% of the exam · 192 questionsDomain 5: AI, and Network Operations and Management10% of the exam · 96 questionsAll CCNA practice questionsMixed sessions across all 5 domains — the way the real exam interleaves them.

IP Routing: your questions

IP Routing is domain 3 of the CCNA exam guide and carries 20% of the scored content — the 3rd-heaviest of the 5 domains. Cisco has not yet published the exam's question count, so there is no per-domain number of questions to give.

Source

The domain weight and topic list on this page come from the official CCNA exam guide.