IPv6 Addressing

Learning objectives

• Explain the purpose and scope of IPv6 Addressing.
• Identify important protocols, roles, fields, and terminology.
• Apply the concept to a practical network scenario.
• Use IOS XE commands to verify operational behavior.

1. Core concepts

IPv6 addresses are 128 bits written as eight groups of four hexadecimal digits. Prefix length identifies the network portion; /64 is common on LANs. IPv6 does not use broadcast; it uses multicast and anycast. Neighbor Discovery uses ICMPv6.

2. How it works

Leading zeros in a hextet may be omitted. One contiguous run of zero hextets may be compressed with :: once. Global unicast is commonly 2000::/3; link-local FE80::/10; unique-local FC00::/7; multicast FF00::/8; loopback ::1; unspecified ::.

Visual walkthrough

3. Worked example

2001:0db8:0000:0000:0000:0000:0042:0001 compresses to 2001:db8::42:1. SLAAC uses Router Advertisements; DHCPv6 may provide addresses or other options, but default-router discovery normally uses Router Advertisements.

IOS XE commands and verification

Syntax and feature availability can vary by device family and software release. Confirm platform support before applying configuration.

ipv6 unicast-routing
interface gigabitEthernet 0/0/0
 ipv6 address 2001:db8:10:1::1/64
 no shutdown
show ipv6 interface brief
show ipv6 route

Common mistakes and troubleshooting

• Check physical and interface state before changing higher-layer settings.
• Verify both ends agree on addressing, VLAN, encapsulation, and protocol parameters.
• Use operational show commands; configured text alone does not prove a feature is working.
• Change one variable at a time and verify the result.

Knowledge check

Choose one answer per question. Submit to see why the correct choice is right and why every other option is wrong. These are original practice questions, not Cisco exam questions.