CCNA IP Routing Practice Question
Exhibit
R1(config)# ?
R1 is an IPv6-only branch router. The administrator wants all unknown IPv6 destinations to be sent to the upstream router at 2001:db8:ff::1. Which command best achieves that goal?
⚠ Common exam trap
A common exam trap is confusing IPv4 and IPv6 routing commands by attempting to use the ip route command with an IPv6 next-hop address. This is invalid because ip route is strictly for IPv4 static routes. Another trap is using ipv6 default-gateway, which is not a valid static routing command and does not install a route in the routing table. These mistakes cause the router to drop unknown IPv6 traffic since no default route is installed. Candidates must recognize that IPv6 static routes require the ipv6 route command with the ::/0 prefix for default routing.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ipv6 route ::/0 2001:db8:ff::1
The correct configuration is an IPv6 default static route pointing to the upstream next hop. In practical terms, this is the IPv6 version of a route of last resort. The router does not need specific entries for every remote IPv6 network if all unknown traffic should go to the upstream device. The key distinction is that IPv6 static routing uses IPv6 syntax and the double-colon default prefix representation. This is a foundational branch-routing concept for IPv6 deployments.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ipv6 route ::/0 2001:db8:ff::1
Why this is correct
This is the correct IPv6 default static route syntax: 'ipv6 route ::/0' matches every IPv6 prefix, and the next hop is the upstream router's global unicast address. The router installs this as a candidate default route, permitting traffic for any destination to be forwarded toward the ISP router when no more specific route matches.
- ✗
ip route 0.0.0.0 0.0.0.0 2001:db8:ff::1
Why it's wrong here
This command is invalid because it mixes IPv4 and IPv6 addressing. The 'ip route' command is exclusively for IPv4 static routes, and its next-hop parameter must be an IPv4 address; supplying the IPv6 address 2001:db8:ff::1 will be rejected by the parser. To configure a static route in an IPv6-only environment, you must use the 'ipv6 route' command.
When this WOULD be correct
In a scenario where the question specifies an IPv4 router needing to route all unknown IPv4 destinations to a specific IPv6 address, this command could be correct if the router supports dual-stack configurations and can handle IPv4 routes to IPv6 addresses.
- ✗
ipv6 route 2001:db8:ff::/64 ::1
Why it's wrong here
This command creates a static route to the specific prefix 2001:db8:ff::/64, not a default route, so it only enables reachability to that one network. Additionally, the next-hop address ::1 (the IPv6 loopback) would be illogical for forwarding out of the router. A default route requires the prefix ::/0 to match all destinations.
When this WOULD be correct
If the question specified that the goal was to route traffic specifically for the subnet 2001:db8:ff::/64 to a local interface or a different router configured at ::1, then option C would be correct as it would direct traffic for that specific subnet appropriately.
- ✗
ipv6 default-gateway 2001:db8:ff::1
Why it's wrong here
This command is not a valid Cisco IOS configuration; the IPv6 routing table is populated via 'ipv6 route' statements, not a default-gateway directive. The 'ip default-gateway' command exists only for IPv4 management on layer-2 switches, and there is no 'ipv6 default-gateway' equivalent for routers. A default route must be installed with 'ipv6 route ::/0'.
When this WOULD be correct
If the question were about configuring a default gateway for an IPv4 router that also supports IPv6, and the goal was to set a default gateway for IPv4 traffic, then 'ipv6 default-gateway 2001:db8:ff::1' could be correct if the router had dual-stack capabilities.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓ipv6 route ::/0 2001:db8:ff::1Correct answer▾
Why this is correct
This is the correct IPv6 default static route syntax: 'ipv6 route ::/0' matches every IPv6 prefix, and the next hop is the upstream router's global unicast address. The router installs this as a candidate default route, permitting traffic for any destination to be forwarded toward the ISP router when no more specific route matches.
✗ip route 0.0.0.0 0.0.0.0 2001:db8:ff::1Wrong answer — click to see why▾
Why this is wrong here
The command 'ip route' is used for IPv4 static routes, not IPv6. Additionally, the syntax '0.0.0.0 0.0.0.0' is an IPv4 default route, but the next hop is an IPv6 address, which is invalid. IPv6 static routes require the 'ipv6 route' command.
★ When this WOULD be the correct answer
In a scenario where the question specifies an IPv4 router needing to route all unknown IPv4 destinations to a specific IPv6 address, this command could be correct if the router supports dual-stack configurations and can handle IPv4 routes to IPv6 addresses.
Why candidates choose this
Students may confuse the IPv4 default route syntax with IPv6, or think that the 'ip route' command can accept an IPv6 next hop. The similarity in concept (default route) makes this option tempting.
✗ipv6 route 2001:db8:ff::/64 ::1Wrong answer — click to see why▾
Why this is wrong here
This command creates a static route for the specific prefix 2001:db8:ff::/64, not a default route. The next hop ::1 is the IPv6 unspecified address (loopback), which is incorrect for forwarding to an upstream router. It does not match the requirement of sending all unknown destinations.
★ When this WOULD be the correct answer
If the question specified that the goal was to route traffic specifically for the subnet 2001:db8:ff::/64 to a local interface or a different router configured at ::1, then option C would be correct as it would direct traffic for that specific subnet appropriately.
Why candidates choose this
A student might think that specifying a route to the upstream network is sufficient, or confuse the unspecified address ::1 with a valid next-hop address. The presence of 'ipv6 route' and an IPv6 address may seem plausible.
✗ipv6 default-gateway 2001:db8:ff::1Wrong answer — click to see why▾
Why this is wrong here
The 'ipv6 default-gateway' command is used on hosts, not routers. On a Cisco router, the correct way to set a default route is with 'ipv6 route ::/0 <next-hop>'. This command does not exist in router IOS for static routing.
★ When this WOULD be the correct answer
If the question were about configuring a default gateway for an IPv4 router that also supports IPv6, and the goal was to set a default gateway for IPv4 traffic, then 'ipv6 default-gateway 2001:db8:ff::1' could be correct if the router had dual-stack capabilities.
Why candidates choose this
The term 'default-gateway' is commonly used in host networking, and students may mistakenly apply it to routers. The IPv6 prefix and next-hop address look correct, making it tempting for those unfamiliar with router configuration.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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OSPFv3 Single-Area Configuration for IPv6
Key term
IPv6
IPv6 is the most recent version of the Internet Protocol, designed to replace IPv4 by providing a vastly larger number of unique addresses and improved network features.
Key term
Route
A route is a path that data takes through a network from one device or network to another, determined by routing protocols and configured rules.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.