IT Connect
Your connection to information technology at the UW

IPv6 Next Generation Internet Protocol

What is IPv6?

IPv6 is the next generation Internet Protocol replacing the current IPv4. It was designed a long time ago, but the worldwide depletion of available IPv4 address space has brought it to the forefront as the future of the internet. IPv6 widens the available address space by several magnitudes, expanding the current 32 bit IPv4 address header to 128 bits. Ideally, a casual internet user will not notice a shift to IPv6 and most devices produced recently are already IPv6 capable, but there could be many considerations for the IT professional operating in the IPv6 environment.

It should be noted that IPv4 addresses will very likely remain in use for the foreseeable future, but it is expected that by 2015 most, if not all, of the new address space allocated by UW-IT will be IPv6.

UW-IT encourages the University’s IT community to begin familiarizing themselves with IPv6 and how it may impact future networking requirements.

UW-IT is currently offering IPv6 space on campus networks to IT organizations by request. For details, send email to or submit a question with the Send a Question to UW-IT form.

Why Implement IPv6?

The University is implementing IPv6 to expand network connectivity options in anticipation of the worldwide depletion of IPv4 address space.

IPv6 Implementation

The University is currently allocating IPv6 address space by department request, or as suggested to certain departments by UW-IT based on subnet scale and familiarity with the protocol. IPv6 will also be “dual stacked” on IPv4 networks and will not be allocated on a per port basis, meaning an individual will be required to work through subnet contacts in order to obtain an IPv6 address. Required use of IPv6 and widespread rollout to campus will be planned according to the remaining supply of IPv4. This is not expected to take place until 2014 or 2015.

An important note in IPv6 implementations is the way in which addresses are handled. A single IPv4 interface gets a single IPv4 address in most instances. Whereas each IPv6 interface can have multiple IPv6 addresses, and each is associated with a scope, which determines the range of hosts that the address can reach. There are 3 main types:

IPv6-capable interfaces are all assigned a “link-local” address, which is only valid for communications on the local subnet – those that never make use of the default gateway. This address will be present even if the network is not enabled for IPv6. The link-local address is used for local communications such as auto-assignment of additional IPv6 addresses. Link-local addresses are assigned from the range fe80::/10 (all link-local addresses will start with fe80:).
Global Scope
The second main type of addresses are those with global scope. This address is the one that must be present for communication with any host outside the UW network. UW’s global IPv6 allocation is 2607:4000::/32. All UW addresses with global scope will start with the 2607:4000: prefix.
Unique Local Address
Finally, a subnet may be allocated a Unique Local Address, or ULA. These addresses are similar to the private address spaces of IPv4, also known as “RFC 1918” addresses, or on the UW campus, “p172”. A ULA address is only valid within its own network. Unlike the “p172” space, there are no plans to apply network address translation (NAT) to allow hosts with only ULA addresses assigned to reach global destinations. ULA addresses can reach globally scoped addresses on the same network. ULA’s are assigned from the range fc00::/7; a pseudo-random number is assigned as part of the address to decrease the likelihood that another organization will use the same range. The ULA range UW has chosen is fd73:a9bd:11bb::/48. You may request a ULA prefix instead of, or in addition to, a global IPv6 prefix for your network.

There have been additional locally scoped address schemes that were proposed but later deprecated. The most commonly referenced is “site-local” addressing, which assigns a block for local access within a particular network. Site-local addressing was abandoned in favor of the ULA scope.

Technical Details

  • UW-IT supports IPv6 address assignment via Stateless Autoconfiguration, also known as SLAAC. With SLAAC assignments the router announces a local prefix, and each host automatically picks an address within that prefix. Customers can also choose not to have the router advertise any prefix and assign addresses manually. When requesting IPv6 address assignment, please specify “without SLAAC” if you wish to assign addresses manually.
  • All address assignments will be /64 blocks. No justification is necessary to receive a /64 for any given network. The router’s IP address will always be the first address in the /64, i.e. 2607:4000:100::1.
  • DHCP address assignment for IPv6 addresses will not be supported in this phase of IPv6 deployment. The DHCPv6 standard was slow to be finalized and ratified, and not all common operating systems yet support DHCPv6. In addition the router support for DHCPv6 is incomplete. As adoption of the standard becomes more widespread UW-IT will establish and support IPv6 addressing via DHCP. Customers can set up a DHCPv6 server on their own subnet if desired.
  • Wireless, Medicine, and Resident Hall networks are not being offered IPv6 at this time.

More Information

Below is a series of informative links. The top link connects to a page entitled ‘Customer problems that could occur’ (right side of the page under ‘How do I prepare’). This may help provide you with some information on the types of issues that are likely to crop up in your experimentation.