When the subjectAltName extension contains a iPAddress, the address MUST be stored in the octet string in "network byte order," as specified in RFC 791 [RFC 791]. The least significant bit (LSB) of each octet is the LSB of the corresponding byte in the network address. For IP Version 4, as specified in RFC 791, the octet string MUST contain exactly four octets. For IP Version 6, as specified in RFC 1883, the octet string MUST contain exactly sixteen octets [RFC 1883].

When the subjectAltName extension contains an iPAddress, the address

MUST be stored in the octet string in "network byte order", as

specified in [RFC791]. The least significant bit (LSB) of each octet

is the LSB of the corresponding byte in the network address. For IP

version 4, as specified in [RFC791], the octet string MUST contain

exactly four octets. For IP version 6, as specified in

[RFC2460], the octet string MUST contain exactly sixteen octets.

The syntax of iPAddress MUST be as described in Section 4.2.1.6 with

the following additions specifically for name constraints. For IPv4

addresses, the iPAddress field of GeneralName MUST contain eight (8)

octets, encoded in the style of RFC 4632 (CIDR) to represent an

address range [RFC4632]. For IPv6 addresses, the iPAddress field

MUST contain 32 octets similarly encoded. For example, a name

constraint for "class C" subnet 192.0.2.0 is represented as the

octets C0 00 02 00 FF FF FF 00, representing the CIDR notation

192.0.2.0/24 (mask 255.255.255.0).

The use of IP addresses

in URLs SHOULD be avoided whenever possible (see RFC 1900 [24]).