IPv6 Questions and Answers

Answer: C

An IPv6 address is 128 bits long.

IPv6 was designed to replace IPv4's 32-bit addresses, whose supply of about 4.3 billion addresses was running out. Its 128-bit addresses, written as eight groups of four hexadecimal digits, allow about 3.4 × 10³⁸ addresses.

32 bits is the IPv4 address size, 64 bits is the size of the interface identifier half of an IPv6 address, and 256 bits is not used.

Answer: B

Tunneling works by encapsulating IPv6 packets inside IPv4 packets.

At the edge of an IPv4-only region, a tunnel endpoint places the entire IPv6 packet inside the payload of an IPv4 packet (marked as protocol 41) and sends it across. IPv4 routers forward it like any other IPv4 packet. The far endpoint removes the IPv4 header and passes on the original IPv6 packet unchanged. 6in4, 6to4 and ISATAP all work this way.

Converting IPv6 headers into IPv4 headers is translation (for example NAT64), a different transition method. Broadcasting is not used at all, IPv6 having no broadcast, and removing IPv4 routing entries would break the network the tunnel relies on.

Answer: D

An IPv6 address has 128 bits.

IPv6 addresses are 128 bits long, written as eight groups of four hexadecimal digits, giving about \(3.4 \times 10^{38}\) addresses, enough to solve IPv4's shortage.

32 bits is the length of an IPv4 address. 64 bits is the size of the interface identifier part of an IPv6 address, not the whole address, and 16 bits is one group.

IPv4's 32 bits allow only about 4.3 billion addresses, which ran out as the internet grew.

Answer: C

Dual stack means the node has both IPv4 and IPv6 support.

Dual stack is one of the strategies for the move from IPv4 to IPv6: a host or router runs both protocol stacks side by side, so it can talk IPv4 to IPv4 systems and IPv6 to IPv6 systems, choosing by the destination address.

It does not mean two copies of the same protocol, so 'IPv4 with 2 stacks' and 'IPv6 with 2 stacks' are wrong. Tunnelling and header translation are the other transition strategies.

Answer: A

Correct answer: Router1(config-if)# ipv6 ospf 10 area 0.0.0.0

OSPFv3 is enabled per interface, giving the process ID and the area in one command, so the prompt must be interface configuration mode. It differs from OSPFv2, which is configured under the routing process with network statements - in version 3 the interface command replaces them entirely.

Answer: B

Correct answer: Router1(config-if)# ipv6 router rip 1

RIPng is enabled on the interface with ipv6 router rip followed by the process name or tag. As with OSPFv3, the routing protocol is turned on where the traffic is rather than by listing networks under the process - which is the general pattern for the IPv6 routing protocols.

Answer: B

Correct answer: FF02::9

RIPng uses FF02::9, which is the IPv6 counterpart of the 224.0.0.9 that RIPv2 used. The link-local multicast group is worth learning as a set: FF02::5 and FF02::6 for OSPFv3, FF02::9 for RIPng, and FF02::A for EIGRPv6.

Answer: D

These addresses are meant for nonrouting purposes like link-local, but they are almost globally unique so it is unlikely they will have an address overlap. Unique local addresses were designed as a replacement for site-local addresses.

Answer: D

Adjacencies and next-hop attributes now use link-local addresses, and OSPFv3 still uses multicast traffic to send its updates and acknowledgments with the addresses FF02::5 for OSPF routers and FF02::6 for OSPF designated routers. These are the replacements for 224.0.0.5 and 224.0.0.6, respectively.

Answer: C

Anycast addresses identify multiple interfaces, which is the same as multicast; however, the big difference is that the anycast packet is only delivered to one address, the first one it finds defined in the terms of routing distance. This address can also be called one-to-one-of-many.