Gentlemen,
I am one of the many Network Engineers/architects that are today on the verge of assigning IPv6 addressing in their core networks.
I initiated a discussion on the use of /64 and /48 addresses in IPv6 and after some debate was convinced or atleast satisfied that for the near/distant future, using /48s and /64s isnt going to cause address depletion. However, there is one point that I would like to open a debate on and really looking for some substantial reasoning and logic on. And this point is: "What is the IETF / IANA / APNIC best-practice / recommendation for assigning IPv6 addressing to strictly point-to-point links where we know there will never be more than one device on each end of the link for the foreseeable future" I have gone through some RFCs (RFC 4291, RFC 5375, RFC 3627, RFC 3177 / 6177 and RFC 6164) As a network engineer with IPv4 and some IPv6 background, I am inclined to use /126 addressing on strictly point to point links - but after discussion with peers in the industry have learnt that the recommendations are to use /64 I want to know rationale behind using a /64 on strictly point-to-point links where we know there will never be more than one device on each end of the link? To me using something like a /126 saves and eases the management / support of the p2p links and gives it more predictability and control. There are conflicting recommendations and are not giving me the right direction e.g.:
RFC 4291 states: "For all unicast addresses, except those that start with the binary value 000, Interface IDs are required to be 64 bits long and to be constructed in Modified EUI-64 format."
RFC 5375 states: "126-bit subnet prefixes are typically used for point-to-point links similar to a the IPv4 address-conservative /30 allocation for point-to-point links. The usage of this subnet address length does not lead to any considerations beyond those discussed earlier in this section, particularly those related to the 'u' and 'g' bits (see B.2.4.)
..... it is recommended to take the 'u' and 'g' bits into consideration and to make sure that there is no overlap with any of the following well-known addresses: o Subnet Router Anycast Address o Reserved Subnet Anycast Address o Addresses used by Embedded-RP o ISATAP Addresses" I guess what I am looking for is some guidelines on why using subnet length greater than /64 is discouraged and whether there is likelihood that any future implementation (of protocol stacks) of IPv6 could create problems for deployments where engineers/architects have chosen to implement /126 on strictly p2p links
Regards
Usman
--- On Sun, 18/9/11, Usman Latif <osmankh at yahoo dot com> wrote:
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