IPv6 Drill 3

 In IPv6 Address Drills

For this next IPv6 addressing drill, you begin with a prefix configured on a router LAN interface using the ipv6 address prefix-id/64 eui-64 command. Your job: calculate the Global Unicast Addresses (GUA) and Link-Local Address (LLA) used on the interface using EUI-64 rules.

This post has both the questions and the answers – just click the items in the post to reveal.

All about IPv6 Drills

IPv6 addresses take up a lot of space – as many as 32 hex digits. Devices help us humans by listing the abbreviated form of IPv6 addresses. However, it helps to think about IPv6 addresses in their unabbreviated (expanded) form – so you need to be skilled at mentally converting from expanded to abbreviated form.

Beyond basic address abbreviation and expansion, you need to be ready to perform other operations on IPv6 addresses, like these:

  • Find the subnet (prefix) ID based on an address (both in abbreviated and expanded form.)
  • Calculate the complete IPv6 address when using the EUI-64 process to build the address’s interface ID (IID) portion.
  • Build Link-Local Addresses (LLAs) based on the MAC address of an interface.

Background: IPv6 Address Drills

IPv6 hosts and routers must use at least one Link-Local Addresses (LLA) on each interface. Originally, devices formed their LLAs using a standard 16-digit prefix (fe80:0000:0000:0000) along with a 16-digit interface ID (IID) formed from the interface MAC address using EUI-64 rules. Today, some devices use a randomization process to find the IID, but some still use EUI-64, including Cisco routers. So, you need to understand the EUI-64 process for LLAs.

When using the eui-64 keyword on the ipv6 address interface subcommand, Cisco routers calculate the IID (2nd half) of a routable unicast address(es) using EUI-64 rules. In short, the configuration supplies the prefix (the first 16 digits), and the router calculates the IID using EUI-64 rules and the interface MAC address.

Instructions and Problems

The following table lists a problem number, a GUA prefix, and a MAC address. From that data, calculate:

  1. The expanded GUA, using EUI-64 rules
  2. The abbreviated version of that same GUA
  3. The expanded LLA, using EUI-64 rules
  4. The abbreviated version of that same LLA


Question Set:

Problem # GUA Prefixes MAC Addresses
1 2001:0db8:1234:009F::/64 0200.1234.5678
2 2001:0db8:bade:0200::/64 0055.abcd.ef12
3 3000:00ba:0000:0000::/64 0600.ba98.6543
4 3000:00ba:0000:000a::/64 0200.cdef.fedc
5 2001:0db8:bade:0000::/64 0200.8765.4321

Lab Answers Below: Spoiler Alert

Click the tabs below to see the answer to each problem.


Answer: Problem 1

Prefix (given) 2001:0db8:1234:009F::/64
MAC (given) 0200.1234.5678
LLA (expanded) fe80:0000:0000:0000:0000:12ff:fe34:5678
LLA (abbreviated) fe80::12ff:fe34:5678
GUA (expanded) 2001:0db8:1234:009F:0000:12ff:fe34:5678
GUA (abbreviated) 2001:db8:1234:9F:0:12ff:fe34:5678

Answer: Problem 2

Prefix (given) 2001:0db8:bade:0200::/64
MAC (given) 0055.abcd.ef12
LLA (expanded) fe80:0000:0000:0000:0255:abff:fecd:ef12
LLA (abbreviated) fe80::255:abff:fecd:ef12
GUA (expanded) 2001:0db8:bade:0200:0255:abff:fecd:ef12
GUA (abbreviated) 2001:db8:bade:200:255:abff:fecd:ef12


Answer: Problem 3

Prefix (given) 3000:00ba:0000:0000::/64
MAC (given) 0600.ba98.6543
LLA (expanded) fe80:0000:0000:0000:0400:baff:fe98:6543
LLA (abbreviated) fe80::400:baff:fe98:6543
GUA (expanded) 3000:00ba:0000:0000:0400:baff:fe98:6543
GUA (abbreviated) 3000:ba::400:baff:fe98:6543

Answer: Problem 4

Prefix (given) 3000:00ba:0000:000a::/64
MAC (given) 0200.cdef.fedc
LLA (expanded) fe80:0000:0000:0000:0000:cdff:feef:fedc
LLA (abbreviated) fe80::cdff:feef:fedc
GUA (expanded) 3000:00ba:0000:000a:0000:cdff:feef:fedc
GUA (abbreviated) 3000:ba:0:a:0:cdff:feef:fedc

Answer: Problem 5

Prefix (given) 2001:0db8:bade:0000::/64
MAC (given) 0200.8765.4321
LLA (expanded) fe80:0000:0000:0000:0000:87ff:fe65:4321
LLA (abbreviated) fe80::87ff:fe65:4321
GUA (expanded) 2001:0db8:bade:0000:0000:87ff:fe65:4321
GUA (abbreviated) 2001:db8:bade::87ff:fe65:4321

Labs with Related Content!

IPv6 Drill 2
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