In IPv6 EIGRP (EIGRP for IPv6), which link-local multicast address is used by EIGRPv6 for sending routing updates and neighbor messages?

Introduction / Context:
Routing protocols that run over IPv6 use specific multicast addresses to communicate with neighbors instead of broadcasting to all nodes. EIGRP for IPv6, also called EIGRPv6, uses a particular link local multicast address to send its hello packets, updates, and other control messages. Recognizing these multicast addresses is a common requirement in certification exams.

Given Data / Assumptions:

• We are dealing with EIGRP for IPv6, not RIPng or OSPFv3.
• The question asks specifically for the multicast address used by EIGRPv6.
• All options are link local IPv6 multicast addresses beginning with FF02::.
• Each multicast address in the options is used by a different protocol or group.

Concept / Approach:
In IPv6, EIGRPv6 uses the link local multicast address FF02::A for sending its routing protocol messages to all EIGRP routers on the local link. Other multicast addresses, such as FF02::9, FF02::5, and FF02::6, are reserved for different purposes, including other routing protocols. Therefore, the correct answer is the one that matches the documented EIGRPv6 multicast group.

Step-by-Step Solution:
1. Recall that EIGRPv6 uses a special IPv6 multicast address to reach all EIGRP neighbors on a link.2. Memorize that FF02::A is the standard multicast address for all EIGRP routers in IPv6.3. Compare this knowledge with the options given.4. Identify that option A, FF02::A, is the exact address associated with EIGRPv6.5. Select FF02::A as the correct multicast address for EIGRPv6.

Verification / Alternative check:
On a Cisco router configured with EIGRP for IPv6, a packet capture on the interface will show hello packets and updates sent to FF02::A. Cisco documentation and IPv6 reference materials explicitly list FF02::A as the multicast group used by EIGRP in an IPv6 environment.

Why Other Options Are Wrong:
Option B, FF02::9, is used by RIPng, not EIGRPv6. Options C and D, FF02::5 and FF02::6, are used by OSPFv3 (all OSPF routers and all OSPF designated routers respectively). These addresses are associated with different IPv6 routing protocols and therefore are not correct for EIGRPv6.

Common Pitfalls:
Because many IPv6 multicast addresses look similar, it is easy to confuse them or assume they are interchangeable. A good strategy is to memorize a small number of important ones, such as FF02::1 for all nodes, FF02::2 for all routers, FF02::5 and FF02::6 for OSPFv3, FF02::9 for RIPng, and FF02::A for EIGRPv6. This reduces guesswork during exams and troubleshooting.

Final Answer:
FF02::A