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Diffstat (limited to '')
| -rw-r--r-- | man/systemd.network.xml | 44 |
1 files changed, 32 insertions, 12 deletions
diff --git a/man/systemd.network.xml b/man/systemd.network.xml index d61e3472c1..a88b6a447d 100644 --- a/man/systemd.network.xml +++ b/man/systemd.network.xml @@ -308,18 +308,38 @@ <varlistentry> <term><varname>IPv6Token=</varname></term> <listitem> - <para>Specifies an optional address generation mechanism and an optional address prefix. If - the mechanism is present, the two parts must be separated with a colon - <literal><replaceable>type</replaceable>:<replaceable>prefix</replaceable></literal>. The - address generation mechanism may be either <constant>prefixstable</constant> or - <constant>static</constant>. If not specified, <constant>static</constant> is assumed. When - set to <literal>prefixstable</literal> a method for generating IPv6 Interface Identifiers to - be used with IPv6 Stateless Address Autocon figuration (SLAAC). See - <ulink url="https://tools.ietf.org/html/rfc7217">RFC 7217</ulink>. When IPv6 address is set, - indicates the 64-bit interface part of SLAAC IPv6 addresses for this link.</para> - - <para>Note that the token is only ever used for SLAAC, and not for DHCPv6 addresses, even in - the case DHCP is requested by router advertisement. By default, the token is autogenerated. + <para>Specifies an optional address generation mode and a required IPv6 address. If + the mode is present, the two parts must be separated with a colon + <literal><replaceable>mode</replaceable>:<replaceable>address</replaceable></literal>. The + address generation mode may be either <constant>prefixstable</constant> or + <constant>static</constant>. If not specified, <constant>static</constant> is assumed. + </para> + <para>When the mode is set to <constant>static</constant>, or unspecified, the lower bits of + the supplied address are combined with the upper bits of a prefix received in a Router Advertisement + message to form a complete address. Note that if multiple prefixes are received in an RA message, or in + multiple RA messages, addresses will be formed from each of them using the supplied address. This + mode implements SLAAC but uses a static interface identifier instead of an identifier generated + using the EUI-64 algorithm. Because the interface identifier is static, if Duplicate Address Detection + detects that the computed address is a duplicate (in use by another node on the link), then this + mode will fail to provide an address for that prefix. + + Note that if multiple <constant>static</constant> IPv6Token variables are supplied, only the first + one will be used to generate addresses. + </para> + <para>When the mode is set to <literal>prefixstable</literal> the RFC 7217 algorithm for generating + interface identifiers will be used, but only when a prefix received in an RA message matches the supplied address. + See <ulink url="https://tools.ietf.org/html/rfc7217">RFC 7217</ulink>. Prefix matching will be attempted + against each <constant>prefixstable</constant> IPv6Token variable provided in the configuration; if a received + prefix does not match any of the provided addresses, then the EUI-64 algorithm will be used to form + an interface identifier for that prefix. This mode is also SLAAC, but with a potentially stable interface + identifier which does not directly map to the interface's hardware address. + + Note that the <constant>prefixstable</constant> algorithm includes both the interface's name and + MAC address in the hash used to compute the interface identifier, so if either of those are changed the resulting + interface identifier (and address) will change, even if the prefix received in the RA message has not changed. + + Note that if multiple <constant>prefixstable</constant> IPv6Token variables are supplied with addresses that + match a prefix received in an RA message, only the first one will be used to generate addresses. </para> </listitem> </varlistentry> |