Scenarios: IPv6 Addresses and Prefix Formats

A help desk worker is troubleshooting a laptop that cannot reach the company file server. The ipconfig output shows only one IPv6 address on the wireless adapter: fe80::3c2a:9bff:fe71:42a8. The default gateway field is blank, and the DHCP server field shows no entry. The user reports that other devices on the same Wi-Fi can reach the server.

What does the fe80:: prefix on the laptop's only IPv6 address indicate about its scope?

• Reserved for one-to-many delivery to grouped receivers

• Assigned from a private range usable across company sites

• Routable across the public internet to any destination

• Usable only for communication on the same local network segment

Answer explanation

Addresses starting with fe80 have link-local scope, meaning they only work between devices on the same segment. They are never routed off the link, which is why the laptop cannot reach the server.

Tags

Blooms Level: Apply

Given the empty gateway and DHCP fields, what is the most likely cause of the connectivity problem?

• The laptop did not receive a routable address from the network

• The fe80 address was manually configured by the user

• The wireless adapter is set to multicast-only mode

• The server is using IPv4 while the laptop uses IPv6

Answer explanation

Every IPv6 interface auto-generates an fe80 address, but a routable address normally comes from DHCPv6 or router advertisements. The blank gateway and DHCP fields show that process did not complete.

Tags

Blooms Level: Analyze

List two troubleshooting steps the help desk worker should try next to help the laptop get a routable IPv6 address.

Tags

Blooms Level: Apply

A network intern is documenting addresses for a new lab subnet. The lead engineer writes the assigned address on the whiteboard as 2400:0f80:00a1:0008:0000:0000:0000:0010 with a /64 mark after it. The intern is asked to record the address in its shortest valid form and to label which portion identifies the subnet versus the interface.

Which is the shortest valid form of 2400:0f80:00a1:0008:0000:0000:0000:0010?

• 2400:f80:a1:8::10

• 2400:f80:a1:8:::10

• 2400:0f80:a1:8::10

• 24:f8:a1:8::10

Answer explanation

Drop leading zeros in each group, then replace the longest run of all-zero groups with a single double colon. Triple colons are never valid, and digits inside a group cannot be removed.

Tags

Blooms Level: Apply

With the /64 mark, which part of the written address identifies the subnet?

• The last four groups of the address

• The first four groups of the address

• The entire 128-bit address value

• Only the very first group, 2400

Answer explanation

A /64 means the leftmost 64 bits, or the first four groups, identify the subnet. The remaining four groups identify the host interface on that subnet.

Tags

Blooms Level: Analyze

Explain in one or two sentences why the run of zero groups in the address can be replaced with :: only once.

Tags

Blooms Level: Understand