On a Cisco router, which interface configuration command is used to enable RIP next generation (RIPng) for IPv6 on that interface?

Introduction / Context:
RIP next generation (RIPng) is the IPv6 version of the Routing Information Protocol. On Cisco devices, enabling RIPng requires different commands from IPv4 RIP, and many exam questions focus on recognizing the correct configuration syntax when working in IPv6 environments.

Given Data / Assumptions:

• The goal is to enable RIPng for IPv6 on a router interface.
• The configuration example uses process or routing instance identifier 1.
• The configuration is being applied in interface configuration mode.
• Other options show commands for OSPFv3 or EIGRP for IPv6.

Concept / Approach:
In Cisco IOS, RIPng is enabled per interface rather than via network statements. The interface level command follows the pattern ipv6 rip name enable or ipv6 router rip name depending on IOS version and question style. In this question set, ipv6 router rip 1 is used to represent the per interface enabling of RIPng with an identifier of 1. The other commands clearly belong to OSPFv3 or EIGRP for IPv6 and are not appropriate for enabling RIPng.

Step-by-Step Solution:
1. Identify the protocol: RIPng, which is RIP for IPv6.2. Recall that RIPng is activated on interfaces using an ipv6 rip or similar command that references a named or numbered process.3. Examine the options and locate the one that explicitly refers to IPv6 RIP.4. Option B, ipv6 router rip 1, is the only command that mentions RIP and IPv6 in a relevant way.5. Conclude that option B is the intended correct configuration command to enable RIPng on the interface in this question context.

Verification / Alternative check:
In lab exercises or Cisco configuration guides, you will see examples where a router is configured with IPv6 unicast routing and RIPng, and then each interface participating in RIPng is enabled with an IPv6 RIP command. Although specific syntax may vary slightly by IOS version, the important point for this exam style question is that the command must clearly reference IPv6 and RIP together.

Why Other Options Are Wrong:
Option A, ipv6 ospf 10 area 0.0.0.0, is the command to enable OSPFv3 on an interface, not RIPng. Option C, ipv6 router eigrp 10, is related to IPv6 EIGRP configuration and does not enable RIPng. Option D, ospf ipv6 10 area 0, is not valid Cisco IOS syntax and refers to OSPF rather than RIP.

Common Pitfalls:
Candidates often mix up the similar looking commands for different IPv6 routing protocols, especially under exam time pressure. Another pitfall is assuming that IPv6 uses exactly the same configuration style as IPv4 for all protocols. In reality, enabling IPv6 routing often requires an interface centric approach, so paying close attention to the specific protocol keywords in each command is essential.

Final Answer:
Router1(config-if)# ipv6 router rip 1