Choose a prefix within its deployment limits
04The Well-Known Prefix and an organization’s Network-Specific Prefix have different operational constraints. A correct bit layout alone does not authorize translation.
With multiple translators, avoid sending a flow to a translator that lacks its state. The source describes distinct prefixes or coordinated state; an address alone is not a session database.
Source for this drawing: RFC 6052 · Read RFC section 3.1 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
The Well-Known Prefix cannot represent non-global IPv4 traffic.
- The Well-Known Prefix cannot represent non-global IPv4 traffic.
- 64:ff9b::/96 MUST NOT represent non-global IPv4 addresses. Translators MUST drop packets using that combination. A published documentation-only format example does not override this restriction.
- Stateless deployments SHOULD assign a Network-Specific Prefix; translatable addresses MUST use it and both address roles SHOULD use the same prefix. Stateful deployments can use either prefix; multiple translators sharing a prefix need coordinated state or distinct prefixes to avoid flow instability.
RFC6052 §3.4 recommends the Well-Known Prefix for stateful scenarios except management-driven NSP choices and the IPv6-Internet-to-IPv4-network scenario, where an NSP MUST be used. Prefix-length recommendations in §3.3 depend on scenario, not one universal /96 rule. RFC8215 separately reserves 64:ff9b:1::/48 for local use; it is not the Well-Known /96 and is not a formal update listed for6052. Rejected errata do not remove u, remove non-global restrictions, or add an exclusive-use MUST.
Read the RFC section ↗