IPv6 Link-Local vs Global Unicast Address
Every IPv6 interface has a link-local address (fe80::/10) that works only on its own link and is never routed. A global unicast address (2000::/3) is optional and carries traffic end to end.
Part of the Subnetting & IP Addressing learning hub. Practice on hands-on CCNA labs.
| At a glance | Link-local | Global unicast |
|---|---|---|
| Prefix | fe80::/10 | 2000::/3 |
| Scope | One link; never routed | Global; routed end to end |
| Required | Yes, on every IPv6 interface | No, optional |
| How it is assigned | Automatically (EUI-64 on Cisco IOS by default), or manually | Statically, with EUI-64, by SLAAC or by DHCPv6 |
| Used for | Neighbor Discovery, router advertisements, routing-protocol next hops | End-to-end traffic |
| Cisco example | ipv6 address fe80::1 link-local | ipv6 address 2001:db8:acad:1::1/64 |
| Pinging it | Needs the outgoing interface | No interface needed |
What a link-local address is
A link-local address comes from fe80::/10 and is valid only on the link it sits on. Routers never forward packets sent to or from it.
Every IPv6-enabled interface gets one automatically; Cisco IOS derives the interface ID with EUI-64 by default. ipv6 address fe80::1 link-local sets one by hand.
IPv6 depends on it. Neighbor Discovery and router advertisements use it, and so do routing protocols: OSPFv3 and EIGRP for IPv6 list neighbors' link-local addresses as next hops.
What a global unicast address is
A global unicast address comes from 2000::/3 and is globally routable. It is the address end-to-end traffic uses.
It is optional: an interface can run IPv6 with only a link-local address. Assign one statically (ipv6 address 2001:db8:acad:1::1/64), with EUI-64 (ipv6 address 2001:db8:acad:1::/64 eui-64), by SLAAC or by DHCPv6. Examples use 2001:db8::/32, the documentation prefix.
Verify and test on Cisco
show ipv6 interface brief lists both addresses on every interface.
To ping a link-local address, specify the outgoing interface: every link has fe80:: addresses, so the router cannot pick one. A global unicast address needs no interface; the routing table decides.
Frequently asked questions
Does every IPv6 interface need a link-local address?
Yes. IPv6 requires one on every interface, and Cisco IOS creates it automatically when IPv6 is enabled. Neighbor Discovery and routing protocols depend on it.
Can an interface run IPv6 without a global unicast address?
Yes. A global unicast address is optional. With only a link-local address, the interface still talks to neighbors on its own link.
Why does pinging a link-local address need an interface?
Every link has its own fe80::/10 addresses, so the router cannot tell which link you mean. Name the outgoing interface and the ping works.
How do I see both addresses on a Cisco router?
Run show ipv6 interface brief. It lists each interface's link-local address and any global unicast addresses.
Now build it
Labs that drill this on real Cisco IOS — configure it yourself, then grade your config against the answer key.
Now configure it on real Cisco IOS
Concepts stick when you configure them. Build one on real Cisco IOS and have your config graded.