Interface ConfigDomain 7.0

ipv6 address [address/prefix]

Assigns a 128-bit IPv6 address to an interface using Classless Inter-Domain Routing (CIDR) slash notation. Unlike IPv4, which rejects traditional subnet masks assigned concurrently on a single port, a single Cisco interface can happily hold dozens of distinct IPv6 addresses simultaneously.

Syntax Breakdown

ipv6 address 2001:0DB8:0000:000A::1/64

CLI Deployment Scenarios

Scenario 1: Manual Global Unicast Provisioning

Deploying a standard, routable Global Unicast address (GUA) with a compressed interface ID.

Router(config)# interface GigabitEthernet0/0

Router(config-if)# ipv6 address 2001:db8:abc:1::1/64

Scenario 2: Hardcoding Link-Local Addresses

By default, the router automatically generates a complex Link-Local address (FE80::) using EUI-64 or random hashes. You can override this to make gateway documentation much easier.

Router(config-if)# ipv6 address fe80::1 link-local

! Downstream endpoints can now point simple traffic explicitly to fe80::1 as their gateway.

CCNA Exam Gotchas

[!]

No Overwrite Behavior

In IPv4, typing a new ip address command automatically overwrites and deletes the old IP on that interface. IPv6 does not do this. If you type a new IPv6 address, it appends to the interface configuration, creating a multi-homed stack. If you made a typo, you must explicitly issue a no ipv6 address [old-address] to clean up the configuration file.