CCNA Network Infrastructure and Connectivity Practice Question
Network Topology
You are connected to R1 via console. The network consists of R1, R2, and a multilayer switch MLS1. R1's GigabitEthernet0/0 connects to MLS1's GigabitEthernet1/0/1 (VLAN 10), and MLS1's GigabitEthernet1/0/2 connects to R2's GigabitEthernet0/0. The goal is to enable IPv6 communication between R1 and R2 across the layer-3 switch. Currently, R1 and R2 cannot ping each other's IPv6 addresses. Configure R1's G0/0 with the IPv6 prefix 2001:db8:1:10::/64 using EUI-64, and R2's G0/0 with static IPv6 address 2001:db8:1:10::2/64. Also ensure MLS1 has IPv6 routing enabled and an IPv6 address on VLAN 10 (2001:db8:1:10::3/64). Troubleshoot and fix any layer-2 or layer-3 issues preventing connectivity.
⚠ Common exam trap
Do not confuse global IPv6 routing enablement with interface address configuration. The presence of a connected route indicates routing is enabled; the missing piece is the interface address. Also, pay attention to specific requirements like EUI-64.
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
✓
Configure 'ipv6 address 2001:db8:1:10::/64 eui-64' on R1's G0/0 interface.
R1 has no IPv6 address configured on G0/0. The required prefix is 2001:db8:1:10::/64 using EUI-64, which generates the interface ID from the MAC address. The command 'ipv6 address 2001:db8:1:10::/64 eui-64' must be entered in interface configuration mode. Additionally, MLS1 has IPv6 routing enabled (as seen by the connected route), but R1's interface is missing the IPv6 address. After configuration, R1 will be able to ping R2 and MLS1. No other changes are needed because R2 and MLS1 are correctly configured.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure 'ipv6 address 2001:db8:1:10::/64 eui-64' on R1's G0/0 interface.
Why this is correct
The correct command uses only the prefix—not a specific interface ID—along with the eui-64 keyword. The router generates the interface ID from its MAC address, producing a unique global unicast address on the required subnet. This matches the requirement to use EUI-64 for R1's configuration.
- ✗
Enable IPv6 routing on R1 with 'ipv6 unicast-routing'.
Why it's wrong here
The command 'ipv6 unicast-routing' enables IPv6 packet forwarding on a router, but the output already indicates that IPv6 routing is active on R1, as evidenced by an existing connected IPv6 route. The real problem is that R1's G0/0 interface has no IPv6 address assigned in the 2001:db8:1:10::/64 subnet, so it cannot participate in IPv6 communication on that link. Enabling routing again is redundant and does nothing to provide the missing interface address, leaving the host unable to reach the router.
- ✗
Configure 'ipv6 address 2001:db8:1:10::1/64' on R1's G0/0 interface (without EUI-64).
Why it's wrong here
The command 'ipv6 address 2001:db8:1:10::1/64' assigns a static, manually defined interface ID (::1) to R1's G0/0 interface. While this would give the interface a valid address in the correct subnet, it violates the explicit requirement to use EUI-64, which derives the interface ID from the MAC address. EUI-64 inserts 'FFFE' in the middle of the MAC and flips the U/L bit, producing a unique address. Without the eui-64 keyword, the router does not perform this derivation, so the configuration would not meet the stated condition.
- ✗
Change the VLAN on MLS1's G1/0/1 to match R1's VLAN.
Why it's wrong here
Changing the VLAN on MLS1's G1/0/1 is unnecessary and would likely cause more harm because the interface is already configured for VLAN 10, which correctly corresponds to the 2001:db8:1:10::/64 subnet. The root cause of the communication issue is not a VLAN mismatch but the absence of an IPv6 address on R1's G0/0 interface. Even if the VLAN is correct, R1 cannot source or forward IPv6 traffic without an address in that subnet. Modifying the VLAN would only disrupt L2 connectivity without addressing the real L3 configuration gap.
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.
✓Configure 'ipv6 address 2001:db8:1:10::/64 eui-64' on R1's G0/0 interface.Correct answer▾
Why this is correct
The correct command uses only the prefix—not a specific interface ID—along with the eui-64 keyword. The router generates the interface ID from its MAC address, producing a unique global unicast address on the required subnet. This matches the requirement to use EUI-64 for R1's configuration.
✗Enable IPv6 routing on R1 with 'ipv6 unicast-routing'.Wrong answer — click to see why▾
Why this is wrong here
IPv6 unicast-routing is already enabled; the problem is at the interface level.
Why candidates choose this
Candidates often assume that IPv6 routing must be enabled globally, but in this scenario it is already configured.
✗Configure 'ipv6 address 2001:db8:1:10::1/64' on R1's G0/0 interface (without EUI-64).Wrong answer — click to see why▾
Why this is wrong here
The requirement specifies EUI-64; omitting it results in a static address that does not match the intended configuration.
Why candidates choose this
Candidates might think a static address is sufficient, but the question mandates EUI-64.
✗Change the VLAN on MLS1's G1/0/1 to match R1's VLAN.Wrong answer — click to see why▾
Why this is wrong here
The VLAN configuration is correct; no change is needed.
Why candidates choose this
Candidates might suspect a layer-2 issue, but the problem is at layer 3 on R1.
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?”
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
Learn chapter
IPv4 Addressing and Address Classes
Key term
VLAN
A VLAN logically segments a physical network into isolated broadcast domains without requiring separate physical switches.
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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JA
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.