IPv6: RFC 6177 obsoletes RFC 3177

In what we believe to be a VERY wise revision, the IETF (Internet Engineering Task Force) has issued RFC 6177 to change the recommendation of indiscriminate issuing of /48 IPv6 address blocks to sites and organizations. Under RFC 3177, end sites were to be given /48 blocks, regardless of size. Thus, if an organization had multiple sites–whether a collection of small doctor’s offices or a multinational conglomerate–each of those sites would be assigned a /48.

Granted, IPv6 provides an unprecedented number of addresses and blocks, but discussions leading up to RFC 6177 argued that such a practice could be tantamount to declaring that 640K of memory is all anyone would ever need. It also was reminiscent of the early days of IPv4 when it wasn’t uncommon to give out /16’s, /12’s or even /8’s to organizations. And we all know how that ended up…

With the publication of RFC 6177 in March 2011, IETF’s recommendation has changed to assignments between /48 and /64, depending on the request. The provision and original intent of RFC 3177 to minimize hurdles in getting sufficient blocks for years ahead has still been preserved, so that end sites can maintain existing subnetting and transition to IPv6 without inordinate difficulties. The allowance, though, to assign a /56 or smaller block where appropriate will help keep IPv6’s options open as use cases and its evolution develops.

Kudos to IETF for learning from history!


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