Connectivity Guide > Connectivity Guide > A. IPv6 Configuration > Parameters for Controlling IPv6 Support > II_TCPIP_VERSION Environment Variable--Specify Version of TCP/IP to Use
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II_TCPIP_VERSION Environment Variable--Specify Version of TCP/IP to Use
The II_TCPIP_VERSION environment variable determines the version of IP addresses that the tcp_ip (or tcp_dec on VMS) protocol driver uses. It can be set using the ingsetenv command.
Note:  The equivalent configuration parameter in config.dat is tcp_ip.version.
This variable has the following format:
II_TCPIP_VERSION = value
value
Controls which tcp_ip protocol driver or which version of IP addresses to use, as one of the following:
ALL
(Default) Uses both IPv4 and IPv6 addresses.
VMS: The default behavior is to use both IPv4 and IPv6 addresses, and to map the IPv4 addresses as IPv6.
6
Uses IPv6 addresses only.
VMS: The IPv6 versions of the listen, accept, and connect are used.
4
Windows: Uses only IPv4 addresses with IPv6-capable functions.
Linux, UNIX, VMS: Uses the IPv4-only version of the protocol driver.
46
Linux and UNIX: Uses only IPv4 addresses with IPv6-capable functions.
Last modified date: 01/30/2023