Change TCP/IP Interface (CHGTCPIFC)

The Change TCP/IP Interface (CHGTCPIFC) command is used to change an existing interface in the Transmission Control Protocol/Internet Protocol (TCP/IP) configuration. The interfaces changed by the CHGTCPIFC command are logical interfaces. They are not physical interfaces. Each interface is associated with a line description. The line description is the physical connection from the system to the TCP/IP network.

The IBM i TCP/IP implementation supports multihoming. This allows either a single interface or multiple interfaces to be specified per line description. The system can appear as any one or combination of the following:

Notes:

  1. In SNMP, an interface is a physical interface. The physical interface relates directly to a TCP/IP interface's line description.
  2. The interface table is shipped with a default IPv4 interface of 127.0.0.1. The line description value associated with the 127.0.0.1 interface is *LOOPBACK. The host table is also shipped with an entry that has an internet address of 127.0.0.1 and host names of LOOPBACK and LOCALHOST.
  3. The interface table is shipped with a default IPv6 interface of ::1. The line description value associated with the ::1 interface is *LOOPBACK. The host table is also shipped with an entry of ::1 and host names of IPV6-LOOPBACK and IPV6-LOCALHOST.

Restrictions:

Parameters

Keyword Description Choices Notes
INTNETADR Internet address Character value, *IP4DHCP, *IP6SAC Optional, Positional 1
LIND Line description Single values: *SAME, *LOOPBACK, *VIRTUALIP, *OPC
Other values: Element list
Optional, Positional 2
Element 1: Line description Name
Element 2: Virtual LAN identifier 1-4094, *NONE
SUBNETMASK Subnet mask Character value, *SAME, *HOST Optional, Positional 3
ADRPFXLEN Address prefix length 1-128, *SAME Optional
ALIASNAME Alias name Simple name, *SAME, *NONE Optional
LCLIFC Associated local interface Character value, *SAME, *NONE Optional
TOS Type of service *SAME, *MINDELAY, *MAXTHRPUT, *MAXRLB, *MINCOST, *NORMAL Optional
MTU Maximum transmission unit 576-16388, *SAME, *LIND Optional
AUTOSTART Autostart *SAME, *YES, *NO Optional
IFCID Interface ID 0000000000000001-FFFFFFFFFFFFFFEF, *SAME, *LIND, *GEN Optional
DADMAXTRN DAD maximum transmits 0-10, *SAME Optional
PVYEXN Privacy extensions *SAME, *NO, *YES Optional
PREFIFC Preferred interfaces Single values: *SAME, *NONE, *AUTO, *DFTROUTE
Other values (up to 10 repetitions): Character value
Optional
PREFLIND Preferred line descriptions Single values: *SAME, *NONE
Other values (up to 10 repetitions): Element list
Optional
Element 1: Line description Name
Element 2: Virtual LAN identifier 1-4094, *NONE
TEXT Text 'description' Character value, *BLANK, *SAME Optional
DHCPDYNDNS DHCP dynamic DNS updates *SAME, *NO, *YES Optional
DHCPCLTID DHCP client identifier *SAME, *ADPTADR, *DHCPUNQID Optional
IP6GENGLBA IPv6 SAC generate global addr *SAME, *YES, *NO Optional

Internet address (INTNETADR)

Specifies the IPv4 or IPv6 internet address.

*IP4DHCP
Specify that Dynamic Host Configuration Protocol is being changed. The LIND parameter must also be specified in order to identify the interface being changed.
*IP6SAC
Specify that IPv6 stateless address auto-configuration is being changed. The LIND parameter must also be specified in order to identify the interface being changed.
character-value
Specify a particular internet address.

An IPv4 internet address is specified in the form nnn.nnn.nnn.nnn, where nnn is a decimal number ranging from 0 through 255. An IPv4 internet address is not valid if it has a value of all binary ones or all binary zeros for the network identifier (ID) portion or the host ID portion of the address.

An IPv6 internet address is specified in the form x:x:x:x:x:x:x:x, where x is a hexadecimal number ranging from 0 through X'FFFF'. "::" may be used once in the IPv6 address to indicate one or more groups of 16 bits of zeros. The "::" may be used to compress leading, imbedded, or trailing zeros in the address.

An IPv6 internet address must be a unicast address and must not contain an imbedded IPv4 address (compatibility or mapped). If *VIRTUALIP is specified for LIND, the IPv6 address must be a global unicast address. If the IPv6 internet address is a link-local unicast address, the line description (LIND) parameter must also be specified in order to identify the interface being changed.

If the internet address is entered from a command line, the address must be enclosed in apostrophes.

Note: If an internet address is not provided with the command, the alias name must be provided and it will be used as the key value for the command.

Line description (LIND)

Specifies the name of the line description associated with the interface being changed. The line description must exist before the TCP/IP interface can be changed.

The following conditions are based on the type of line description:

Ethernet
The line description must be previously created with the Create Line Description (Ethernet) (CRTLINETH) command.

Single values

*SAME
The value does not change.
*LOOPBACK
The interface being changed is the loopback or LOCALHOST interface. Because processing associated with loopback does not extend to a physical line, there is no line description associated with a loopback address. This special value must be used for any INTNETADR that has a first octet value of 127.
*VIRTUALIP
The virtual interface is a circuitless interface. It is used in conjunction with the associated local interface (LCLIFC) when adding standard interfaces. This special value is used to accommodate any of the following cases:
  1. Load balancing. This is the means of having a fixed source IP address regardless of which interface the traffic is being distributed.
  2. Alternate method of network access translation (NAT). This eliminates the need for a NAT box by assigning a globally unique single IP address directly to the box without the need to define an entire network.
  3. Unnumbered networks. This provides a means of associating a local source IP address for an unnumbered point-to-point network.
*OPC
This special value is used if a TCP/IP over OptiConnect interface is being changed. This interface is attached to the optical bus (OptiConnect). INTNETADR must specify an IPv4 address.

Element 1: Line description

name
Specify the name of the line description to be used for this interface. If INTNETADR specifies an IPv6 address or *IP6SAC, the line description must be for an Ethernet line. A line description name is required if INTNETADR is *IP4DHCP.

Element 2: Virtual LAN identifier Specifies the virtual LAN identifier of the associated line. This identifies the virtual LAN to which this interface belongs according to IEEE standard 802.1Q. This parameter is only valid for interfaces defined for Ethernet adapters that support the 802.1Q standard.

*NONE
Start of change
This interface is not part of a virtual LAN or belongs to the native VLAN of the associated line.End of change
1-4094
Specify the virtual LAN identifier of the associated line.

Subnet mask (SUBNETMASK)

Specifies the subnet mask, which is a bit mask that defines the part of the network where this IPv4 interface attaches. The mask is a 32-bit combination that is logically ANDed with the IPv4 internet address to determine a particular subnetwork. The bits of the mask set to the value one (1) determine the network and subnetwork portions of the address. The bits set to the value zero (0) determine the host portion of the address.

The bits that identify the subnetwork are not required to be adjacent in the address. However, if this subnet mask value is changed, it might invalidate or affect the routes using this interface. To prevent this, keep the subnet bits contiguous and located in the most significant bits of the host address.

Note: The network portion must be equal to one bits in the subnetmask. The host portion of an address must be at least two bits wide. This parameter is ignored if INTNETADR specifies an IPv6 address, *IP4DHCP, or *IP6SAC.

*SAME
The value does not change.
*HOST
The subnet mask value used will be 255.255.255.255. Specify this value for use with Proxy ARP (Address Resolution Protocol).
character-value
Specify the mask for the network subnet field and host address field of the internet address that defines a subnetwork. The subnet mask is in the form nnn.nnn.nnn.nnn, where nnn is a decimal number ranging from 0 through 255. The subnet mask must mask off all bits of the network class's network ID portion of the internet address. For more detailed information on subnet masks and an example, see the help for the Add TCP/IP Interface (ADDTCPIFC) command.

Address prefix length (ADRPFXLEN)

Specifies the address prefix length in bits. The address prefix length specifies how much of the leftmost portion of an IPv6 address is the subnet prefix. This parameter applies only if INTNETADR is an IPv6 address.

*SAME
The value does not change.
1-128
Specify the address prefix length.

Alias name (ALIASNAME)

Specifies a name that can be used in place of the internet address. The name must be unique among all of the interfaces on the system.

Note: If an internet address is not provided with the command, the alias name will be the key for the command. If an internet address is provided, the alias name can be changed from its current value.

*SAME
The value does not change.
*NONE
No alias name is associated with the TCP/IP interface being changed.
simple-name
Specify an alias for the interface. The alias name must be 25 characters or less.

Associated local interface (LCLIFC)

Use this parameter to associate the IPv4 interface being changed with an existing local IPv4 TCP/IP interface. This parameter is ignored if INTNETADR specifies an IPv6 address, *IP4DHCP, or *IP6SAC.

The associated local interface (LCLIFC) is used to allow 'transparent subnetting' (also known as 'Proxy Arp') between the associated interfaces, to define unnumbered networks, or for load balancing.

Conditions for using the LCLIFC for unnumbered networks:

Conditions for using LCLIFC for transparent subnetting:

Condition for using the LCLIFC for load balancing:

Note: LCLIFC can only be used to associate this interface with another interface that is already added. Once associated, the interface specified in LCLIFC and this interface must both be started in order for them to work together properly.

*SAME
The value does not change.
*NONE
No TCP/IP interface is associated with the interface being changed.
character-value
Specify the internet address of the interface you want to associate with the interface being changed.

Type of service (TOS)

Specifies the type of service to be used. The type of service specifies how the internet hosts and routers should make trade-offs between throughput, delay, reliability, and cost. This parameter is ignored if INTNETADR specifies an IPv6 address, *IP4DHCP, or *IP6SAC.

*SAME
The value does not change.
*NORMAL
Normal service is used for delivery of data.
*MINDELAY
Minimize delay means that prompt delivery is important for data on this connection.
*MAXTHRPUT
Maximize throughput means that a high data rate is important for data on this connection.
*MAXRLB
Maximize reliability means that a higher level of effort to ensure delivery is important for data on this connection.
*MINCOST
Minimize monetary cost means that lower cost is important for data on this connection.

Maximum transmission unit (MTU)

Specifies the maximum size (in bytes) of IP datagrams that can be transmitted through this interface. A datagram is a basic unit of information passed over an internet network. For an IPv4 interface, the minimum MTU value is 576 bytes. For an IPv6 interface, the minimum MTU value is 1280 bytes. If this value is changed it affects the MTUs of routes using this interface.

*SAME
The value does not change.
*LIND
The MTU is determined by the information specified in the line description. If *LIND is specified, the MTU is equal to the largest amount of data that can be transmitted on the line.
576-16388
Specify a value for the maximum transmission unit in bytes. The maximum MTU that can be specified for this interface depends on the type of physical connection to the network. The following table lists the maximum MTU values that can be specified based on the line type:
Ethernet 802.3
8992
Ethernet Version 2
9000

Notes:

  1. The actual MTU value used for an interface is resolved during interface activation. This value is the minimum of either the specified MTU value for the interface or the largest amount of data that can be transmitted on the line.
  2. It is suggested (not required) that the same MTU values be used for all interfaces on the same network. However, all interfaces must have an MTU that does not exceed the value used when *LIND is specified for the interface MTU.
  3. To view the MTU value actually used for an interface, do the following:
    1. Use the Start TCP/IP Interface (STRTCPIFC) command to activate the interface.
    2. Use the Work with TCP/IP Status (WRKTCPSTS or NETSTAT) command to view the actual MTU value of the interface in bytes.

Autostart (AUTOSTART)

Specifies whether the interface is automatically started when the TCP/IP stack is activated by the Start TCP/IP (STRTCP) command.

*SAME
The value does not change.
*YES
The interface is automatically started when TCP/IP is started.
*NO
The interface is not started when TCP/IP is started.

Note: The Start TCP/IP Interface (STRTCPIFC) command can be used to start an interface after TCP/IP has been started.

Interface ID (IFCID)

Specifies the interface ID portion of the IPv6 address(es) generated when INTNETADR is *IP6SAC. The interface ID is the low-order 64 bits of an IPv6 address created as a result of IPv6 stateless address auto-configuration.

*SAME
The value does not change.
*LIND
Use the local adapter address in the associated line description to generate the interface ID.
*GEN
Generate a random local scope interface ID..
0000000000000001-FFFFFFFFFFFFFFEF
Specify the interface ID to be used.

DAD maximum transmits (DADMAXTRN)

Specifies the maximum number of neighbor solicitation messages to send for IPv6 duplicate address detection (DAD). This parameter applies only if INTNETADR is an IPv6 address or *IP6SAC.

*SAME
The value does not change.
0-10
Specify the number of neighbor solicitation messages to be sent. A value of zero indicates that duplicate address detection is not performed.

Privacy extensions (PVYEXN)

Specifies whether privacy extensions are to be used for IPv6 stateless address auto-configuration. This parameter applies only when INTNETADR is *IP6SAC.

*SAME
The value does not change.
*NO
Do not use privacy extensions.
*YES
Use privacy extensions.

Preferred interfaces (PREFIFC)

Specifies a list of preferred IPv4 interfaces that are to be used with the IPv4 interface being changed for proxy Address Resolution Protocol (ARP) agent selection. The IPv4 interface being changed must have a LIND value of *VIRTUALIP or specify a LIND for a virtual Ethernet line. Up to 10 associated interfaces may be specified in order of preference -- the first being the most preferred, the second the next preferred, etc. Each associated interface must be a standard IPv4 interface, not a virtual interface.

Single values

*SAME
The value does not change.
*NONE
No associated interfaces are specified.
*AUTO
Interface selection is performed automatically by the system.
*DFTROUTE
Interface selection is performed dynamically based on the binding interface of the best, active default IPv4 route on the system.

Other values (up to 10 repetitions)

character-value
Specify the IPv4 address of the preferred interface.

Preferred line descriptions (PREFLIND)

Specifies a list of preferred line descriptions that are to be used with the IPv6 interface being changed for proxy Neighbor Discovery agent selection. The IPv6 interface being changed must have a LIND parameter which specifies *VIRTUALIP or the name of a virtual Ethernet line description. Up to 10 line descriptions and their associated virtual LAN identifier may be specified in order of preference -- the first being the most preferred, the second the next preferred, etc. Each line description and virtual LAN identifier must be used by at least one IPv6 interface.

Single values

*SAME
The value does not change.
*NONE
No preferred line descriptions are specified.

Element 1: Line description

name
Specify the name of the preferred line description.

Element 2: Virtual LAN identifier Specifies the virtual LAN identifier of the associated line. This identifies the virtual LAN to which this interface belongs according to IEEE standard 802.1Q. This parameter is only valid for lines configured for Ethernet adapters that support the 802.1Q standard.

*NONE
The associated line is not part of a virtual LAN.
1-4094
Specify the virtual LAN identifier of the associated line.

Text 'description' (TEXT)

Specifies text that briefly describes the interface.

*SAME
The value does not change.
*BLANK
No text is specified.
character-value
Specify no more than 50 characters of text, enclosed in apostrophes.

DHCP dynamic DNS updates (DHCPDYNDNS)

Specifies whether the DHCP server should update the client's records in the Domain Name Server (DNS). This parameter is ignored unless the INTNETADR parameter is *IP4DHCP or *IP6SAC.

*SAME
The value does not change.
*YES
Specify that the DHCP server should update the client's records in the DNS.
*NO
Specify that the DHCP server should not update the client's records in the DNS.

DHCP client identifier (DHCPCLTID)

Specifies whether the DHCP client uses an identifier based on the hardware address of the interface or the system-wide DHCP unique identifier specified by the TCP/IP attributes. This parameter is ignored unless the INTNETADR parameter is *IP4DHCP.

*SAME
The value does not change.
*ADPTADR
Specify that the DHCP client will use an identifier based on the adapter address of the interface.
*DHCPUNQID
Specify that the DHCP client will use the system-wide DHCP unique identifier.

IPv6 SAC generate global addr (IP6GENGLBA)

Specifies whether IPv6 Stateless Address Auto-configuration (SAC) will generate global addresses for this interface. This parameter is ignored unless the INTNETADR parameter is *IP6SAC.

*SAME
The value does not change.
*YES
Global addresses are generated by IPv6 SAC.
*NO
Global addresses are not generated by IPv6 SAC.

Examples

Example 1: Changing Autostart Value

CHGTCPIFC   INTNETADR('130.14.3.5')  AUTOSTART(*NO)

Assuming that an interface identified by 130.14.3.5 exists, this command changes the autostart value from *YES to *NO. The interface is not automatically started when the STRTCP command is entered.

Example 2: Changing MAXSVC and IDLVCTTIMO

CHGTCPIFC   INTNETADR('8.77.0.21') IDLVCTTIMO(45) MAXSVC(15)

This command changes the idle virtual circuit time-out to 45 seconds and the maximum number of concurrent SVCs allowed to be used by TCP/IP on this interface to 15.

Example 3: Change an Interface for a Twinax Line that is Using an Associated Local Interface

CHGTCPIFC   INTNETADR('199.1.1.99')  LCLIFC('199.1.1.1')

This command will change the TCP/IP interface for the twinax line named TDLCLINE. This interface will be associated with local interface 199.1.1.1. This means that the devices attached to twinax line 199.1.1.99 can take advantage of 'appearing' to be on the same network as the local 199.1.1.1 interface (transparent subnetting). No special routing is required to ensure packets from the twinax connnected hosts can travel to the local 199.1.1.0 network. Also, hosts on the 199.1.1.0 network can also reach the twinax hosts without any additional routing on the host systems.

Example 4: Changing ALIASNAME

CHGTCPIFC   INTNETADR('132.15.7.32')  ALIASNAME(TEST_NETWORK)

This command changes the alias name for this interface to TEST_NETWORK.

Example 5: Changing the interface using the ALIASNAME

CHGTCPIFC   ALIASNAME(TEST_NETWORK)  AUTOSTART(*YES)

This command changes the auto start value for the interface named TEST_NETWORK.

Example 6: Changing an IPv4 Virtual Interface

CHGTCPIFC   INTNETADR('192.168.2.1')
            PREFIFC('192.168.2.2' '192.168.2.3')

This command changes virtual IPv4 interface 192.168.2.1 to have two interfaces as preferred IPv4 interfaces. Interface 192.168.2.2 is preferred over 192.168.2.3. Interface 192.168.2.1 was previously added specifying a LIND value of *VIRTUALIP.

Example 7: Changing an IPv6 Virtual Interface

CHGTCPIFC   INTNETADR('1234::5678')
            PREFLIND(ETHLINE3 ETHLINE1 ETHLINE2)

This command changes virtual IPv6 interface 1234::5678 to have three line descriptions to be used for VIPA proxy Neighbor Discovery agent selection. Line description ETHLINE3 is preferred over ETHLINE1 and ETHLINE2, and ETHLINE1 is preferred over ETHLINE2.

Example 8: Changing the text description of an IPv6 Interface

CHGTCPIFC   INTNETADR('FE80::5678')
            LIND(ETHLINE1 34) TEXT('New text description')

This command changes the text description for IPv6 interface FE80::5678 associated with line description ETHLINE1 and virtual LAN 34.

Error messages

*ESCAPE Messages

TCP1D03
&1 member record length not correct.
TCP1D04
Error occurred processing member &1 of &2/&3.
TCP1901
Internet address &2 not valid.
TCP1902
Internet address &1 not valid.
TCP1908
Internet address &1 not valid.
TCP8050
*IOSYSCFG authority required to use &1.
TCP9999
Internal system error in program &1.