IPv6 Drill 3
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.
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:
- The expanded GUA, using EUI-64 rules
- The abbreviated version of that same GUA
- The expanded LLA, using EUI-64 rules
- 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.
Answers
Answer: Problem 1
| Value | |
| 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
| Value | |
| 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
| Value | |
| 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
| Value | |
| 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
| Value | |
| 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 |
