fe80::/10: IPv6 link-local

Answer

fe80::/10 is the IPv6 link-local range. Every interface that runs IPv6 automatically has an address in it, usually fe80:: followed by a 64-bit interface ID, and it works only on that one link; routers never forward it.

fe80::/10 is 2^118 ≈ 332 decillion addresses: fe80:: to febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff. IPv6 has no broadcast address.

fe800000000000000000000000000000

10-bit prefix 118 bits for subnets and hosts (each hex digit is 4 bits)

Network: fe80::
First address: fe80::
Last address: febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses: 2^118 ≈ 332 decillion
Usable: ≈ 332 decillion
Expanded: fe80:0000:0000:0000:0000:0000:0000:0000
Range type: Link-local unicast · not routed on the internet
/64 subnets inside: 2^54 ≈ 18.0 quadrillion

Special-purpose range

Link-local unicast fe80::/10 RFC 4291
Every IPv6 interface has one (fe80::…). Valid only on the local link; often written with a zone like %eth0.

Split it into subnets

256 subnets, first 16 shown.

Subnet	Range	Addresses
`fe80::/18`	`fe80::1` – `fe80:3fff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe80:4000::/18`	`fe80:4000::1` – `fe80:7fff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe80:8000::/18`	`fe80:8000::1` – `fe80:bfff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe80:c000::/18`	`fe80:c000::1` – `fe80:ffff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe81::/18`	`fe81::1` – `fe81:3fff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe81:4000::/18`	`fe81:4000::1` – `fe81:7fff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe81:8000::/18`	`fe81:8000::1` – `fe81:bfff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe81:c000::/18`	`fe81:c000::1` – `fe81:ffff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe82::/18`	`fe82::1` – `fe82:3fff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe82:4000::/18`	`fe82:4000::1` – `fe82:7fff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe82:8000::/18`	`fe82:8000::1` – `fe82:bfff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe82:c000::/18`	`fe82:c000::1` – `fe82:ffff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe83::/18`	`fe83::1` – `fe83:3fff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe83:4000::/18`	`fe83:4000::1` – `fe83:7fff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe83:8000::/18`	`fe83:8000::1` – `fe83:bfff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion
`fe83:c000::/18`	`fe83:c000::1` – `fe83:ffff:ffff:ffff:ffff:ffff:ffff:ffff`	2^110 ≈ 1.3 decillion

Is this IP in the range?

Range to CIDR blocks

What to know

The range is formally a /10, but RFC 4291 requires the next 54 bits to be zero, so in practice every link-local address is in fe80::/64.

Link-local addresses do real work: routers send router advertisements from them, a host's default gateway is usually the router's fe80:: address, and neighbor discovery uses them. They exist even when no global IPv6 address is configured.

Gotchas

Because every interface has the same fe80::/64 prefix, the system cannot tell which link you mean from the address alone. Add a zone: ping fe80::1%eth0 on Linux, or an interface number on Windows.
Most browsers do not accept link-local addresses with a zone in URLs, so http://[fe80::1%eth0]/ usually does not work for reaching a device's web interface.
An fe80:: address on an interface does not mean IPv6 internet access works. Look for a global address (starting with 2 or 3) as well.

Related explainers

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