IP address formats accepted by CICS

CICS accepts IPv4 and IPv6 addresses in specific formats for processing.

IPv6 address formats

CICS accepts IPv6 addresses in the following format only:
  • As a native IPv6 colon hexadecimal address without square brackets or /nn notation; for example, ::a:b:c:d

IPv6 address syntax is described in more detail in RFC 4291, IP Version 6 Addressing Architecture, available at http://www.ietf.org/rfc/rfc4291.txt.

Double colons in an IPv6 address

The layout of an IPv6 address is defined in RFC 2373, IP Version 6 Addressing Architecture, available at http://www.ietf.org/rfc/rfc2373.txt. This permits the single use of a double colon to mean one or more 0: elements sufficient to make an eight element address.

For example: 1::7:8 means 1:0:0:0:0:0:7:8
The double colon can:
  • Start an IPv6 address, so that ::5:6:7:8 means 0:0:0:0:5:6:7:8
  • End an IPv6 address, so that 1:2:3:4:: means 1:2:3:4:0:0:0:0
  • Be in the middle of an IPv6 address, so that 1:2::6:7:8 means 1:2:0:0:0:6:7:8
There are two special cases for the use of an initial double colon:
  • When using a double colon to specify an IPv4 address in IPv4 compatible format (::1.2.3.4)
  • When using a double colon to specify an IPv4 address in IPv4 mapped format (::FFFF:1.2.3.4)

IPv4 address formats

CICS accepts IPv4 addresses in the following formats:
  • A native IPv4 dotted decimal address without /nn notation; for example, 1.2.3.4
  • An IPv4 address that is migrated to IPv6 format (an IPv4-mapped IPv6 address); for example, ::ffff:1.2.3.4
    • Internally, CICS translates the address into the binary equivalent of 0:0:0:0:0:ffff:0102:0304
  • An IPv6 compatible address (an IPv4-compatible IPv6 address); for example, ::1.2.3.4
    • Internally, CICS translates the address into the binary equivalent of 0:0:0:0:0:0:0102:0304
    This exception applies:
    • CICS does not allow the following entries:
      • 0.0.0.0
      • ::0.0.0.0
      • ::0

Whichever format you specified for your IPv4 address, CICS displays all IPv4 addresses as a native IPv4 dotted decimal address; for example, 1.2.3.4

Specifying an IPv4 address in CICS TS

Certain CICS Transaction Server for z/OS (CICS TS) V4.1, and later, objects require the specification of an IPv4 address in, for example, the HOST field of the object. Here is now to specify different types of IPv4 addresses within CICS TS.

An IPv6 address consists of 8 elements, which are specified in hexadecimal. Each element consists of two hexadecimal bytes with right zero justification. Use of a double colon permits many 0 elements to be compressed.

An example IPv6 address is 1:2:3:4:5:6:7:8, which is processed as 0001:0002:0003:0004:0005:0006:0007:0008

In contrast, there are many ways of supplying an IPv4 address to CICS TS as shown in the following table:

Table 1. IPv4 Addresses. Six options of supplying IPv4 addresses to CICS TS.
Type of specification Examples Specification rules
IPv4 native

1.2.3.4
255.255.255.255
1.02.003.14

 There must be 4 elements that are delimited by dots. Each element must be numeric and be 0 - 255. Leading zeros are acceptable.
IPv4 compatible (in compressed format)

::1.2.3.4
::255.255.255.255
::1.02.003.14

 Starts with a double colon, and then the formatting is as for IPv4 native.
IPv4 compatible

0:0:0:0:0:0:1.2.3.4
0::255.255.255.255
0::00:1.02.003.14

 Elements 1,2,3,4,5 and 6 of the full IPv6 address must evaluate to 0 (with right zero justification). Elements 7 and 8 are formed by using the IPv4 formatting rules.
IPv4 mapped (in compressed format)

::FFFF:1.2.3.4
::ffff:255.255.255.255
::fFfF:1.02.003.14

 Starts with a ::FFFF:, and then the formatting is as for IPv4 native. The FFFF can be in mixed case.
IPv4 mapped

::0:FFFF:1.2.3.4
0:0:0:0:0:FFFF:255.255.255.255
0::FfFf:1.02.003.14

 IPv4 mapped ::0:FFFF:1.2.3.4 0:0:0:0:0:FFFF:255.255.255.255 0::FfFf:1.02.003.14 Elements 1,2,3,4 and 5 of the full IPv6 address must evaluate to 0 (with right zero justification) and elements 6 must be FFFF (in mixed case). Elements 7 and 8 are formed by using the IPv4 native rules.
IPv6 hexadecimal notation

::0:ABCD:EF12
0:0:00:000:0000:0:abCd:eF12
0::aBCD:ef12

 Elements 1,2,3,4,5 and 6 must evaluate to 0 (with right zero justification). Elements 7 and 8 are the IPv4 address that is specified in hexadecimal notification: element 7 is the first two elements of the native IPv4 address and element 8 is third and forth elements of the IPv4 native address. In all of these cases, the IPv4 native address is 171.205.239.18.
Parent topic: IP addresses

dfhtl_ipformats.html | Timestamp icon Last updated: Thursday, 27 June 2019