CHGTCPIFC (Change TCP/IP Interface)

CHGTCPIFC Command syntax diagram

 

Purpose

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 defined 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 iSeries 400 to the TCP/IP network.

The iSeries 400 TCP/IP implementation supports multihoming. This allows you to specify either a single interface or multiple interfaces per line description. You can have your iSeries 400 appear as any one or combination of the following:

• A single host on a network over a communications line
• Multiple hosts on the same network over the same communications line
• Multiple hosts on different networks over the same communications line
• Multiple hosts on the same network over multiple communications lines
• Multiple hosts on different networks over multiple communications lines

 

Notes

1. If you attempt to change a value for an interface that will invalidate a route or remote system information (RSI) associated with the interface, the change will not be allowed.
   
2. In SNMP, an interface is a physical interface. The physical interface relates directly to an input/output processor (IOP).
   
3. The interface table is shipped with a default 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.

Attention:

Before attempting to start an X.25 interface, ensure that the remote system information (RSI) for non-DDN X.25 interfaces that use a permanent virtual circuit (PVC) is configured. Use the Add TCP/IP Remote System Information (ADDTCPRSI) command to do this. Incoming data from a remote system on the X.25 network is not processed unless an RSI entry for the PVC is configured on the X.25 interface before the interface is started.

 

Restrictions

• You must have *IOSYSCFG special authority to use this command.
  
• Only certain values can be changed using this command. The values that can be changed depend on the status of the interface, the status of the dependent routes, and the remote system information configured.

 

Required Parameters

INTNETADR

Specifies the internet address. The internet address is specified in the form nnn.nnn.nnn.nnn, where nnn is a decimal number ranging from 0 through 255. An 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. If the internet address is entered from a command line, the address must be enclosed in apostrophes.

 

Optional Parameters

LIND

Specifies the name of the line description associated with the to be changed interface. The following conditions are based on the interface type that the user defines:

Token-ring

The name must be previously defined on the Create Line Description (Token-Ring Network) (CRTLINTRN) command.

X.25

The name must be previously defined on the Create Line Description (X.25) (CRTLINX25) command.

Ethernet

The name must be previously defined on the Create Line Description (Ethernet) (CRTLINETH) command.

DDI

The name must be previously defined on the Create Line Description (DDI Network) (CRTLINDDI) command.

Frame relay

The name must be previously defined on the Create Line Description (Frame Relay Network) (CRTLINFR) command.

Wireless

The name must be previously defined on the Create Line Description (Wireless Network) (CRTLINWLS) command.

Twinax (TDLC)

The name must be previously defined on the Create Line Description (CRTLINTDLC) command.

TCP/IP can also be used on certain line descriptions attached to these network interfaces (NWI):

• An ISDN NWI using an X.25 line description.

  • The ISDN NWI is created using the Create Network Interface ISDN (CRTNWIISDN) command.
    
  • The X.25 line is created using the Create Line X.25 (CRTLINX25) command and attached to the ISDN NWI by specifying the NWI, NWICHLTYPE, NWICHLNBR, and SWTNWILST parameters.

  
  

• A frame relay NWI using a frame relay, token ring, Ethernet, or DDI line description.

  • The frame relay NWI is created using the Create Network Interface Frame Relay Network (CRTNWIFR) command.
    
  • The line description is created using the appropriate Create Line command and attached to the frame relay NWI by specifying the NWI and NWIDLCI parameters.

*SAME: The same line description existing for this interface is used.

*LOOPBACK: The interface being changed by this command 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 internet address that has a first octet value of 127.

*VIRTUALIP: This special value is used if you are adding a 'circuitless' interface. This means that this interface has a real IP address but is NOT tied to any physical hardware. Interfaces of this type are useful to identify the address of the iSeries 400 to remote systems over point-to-point links (PPP, SLIP, Frame Relay, X.25).

*OPC: This special value is used if you are adding an OptiConnect interface over TCP/IP. This interface is attached to the optical bus (OptiConnect).

line-description: Specify the line description to be used for this interface.

SUBNETMASK

Specifies the subnet mask, which is a bit mask that defines the part of the network where this interface attaches. The mask is a 32-bit combination that is logically ANDed with the 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.

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.

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.

*SAME: The same subnetmask existing for this interface is used.

*HOST: The subnetmask value used will be 255.255.255.255. *HOST is not valid for X.25 interfaces.

subnet-mask: Specify the mask for the network 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 Add TCP/IP Interface (ADDTCPIFC) command description.

LCLIFC

The local IP interface that the internet address defined in INTNETADR will be associated with.

The associated local interface is used to allow for transparent subnetting or unnumbered networks on the iSeries 400. Any local interface may be used for LCLIFC, except for interfaces defined for the X.25 or PPP linetypes.

*SAME: The current associated local interface is used.

*NONE: No associated local interface is used.

local-interface: Specify an associated local interface for the interface being changed. Note that the specified associated local interface must already exist.

TOS

Specifies the type of service to be used. The type of service defines how the internet hosts and routers should make trade-offs between throughput, delay, reliability, and cost.

*SAME: The type of service 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.

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. The minimum size of any maximum transmission unit value is 576 bytes. If this value is changed it affects the MTUs of routes using this interface.

*SAME: The existing maximum transmission unit value for this interface is used.

*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. If the LIND parameter specifies *LOOPBACK, *VIRTUALIP, or *OPC, then the MTU value will be:

*LOOPBACK

576

*VIRTUALIP

576

*OPC

32768

maximum-transmission-unit: 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:

X.25

4096

Token ring (4 meg)

4060

Token ring (16 meg)

16388

Ethernet 802.3

1492

Ethernet Version 2

1500

DDI

4352

Frame relay

8177

Wireless 802.3

1492

Wireless Version 2

1500

Twinax (TDLC)

4105

 

Notes

1. It is suggested that the same MTU values be used for all interfaces on the same network.
   
2. 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.
   
3. The same MTU value does not need to be specified for all interfaces defined on the same subnet. However, all interfaces must have an MTU that does not exceed the value used when *LIND is specified for the interface MTU.
   
4. To view the MTU value actually used for an interface, do the following:

   1. Use the ADDTCPIFC command to add the interface.
      
   2. Use the Start TCP/IP Interface (STRTCPIFC) command to activate the interface.
      
   3. Use the Work with TCP/IP Status (WRKTCPSTS or NETSTAT) command to view the actual MTU value of the interface in bytes.

AUTOSTART

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

*SAME: The existing autostart value for this interface is used.

*YES: The interface is automatically started at STRTCP time.

*NO: The interface is not started at STRTCP time.

Note:

The Start TCP/IP Interface (STRTCPIFC) command can be used to start an interface any time after TCP/IP has been activated.

PVCLGLCHLI

Specifies the permanent virtual circuit (PVC) logical channel identifiers that can be established on an X.25 interface by the TCP/IP protocol stack. Up to 64 unique channel identifiers may be specified. These logical channel identifiers must exist in the X.25 line description.

With this parameter you can share the line with other communications software, such as Systems Network Architecture (SNA). It prevents the TCP/IP protocol stack from monopolizing the PVCs defined for the line.

 

Notes

1. This parameter is valid only for an interface defined on an X.25 line description.
   
2. PVCs cannot be used in a DDN network.
   
3. When specifying PVCs for an X.25 interface, all interfaces on the same X.25 network must have this same set of PVC logical channel identifiers specified. This is especially important if one or more remote system information (RSI) entries will use a PVC to connect to the RSI entry's remote system on the X.25 network.
   
4. If the RSI entries are defined such that two or more remote internet addresses can be reached across the same PVC, that PVC is shared.
   
5. The sum of the maximum switched virtual circuits (MAXSVC) and the number of PVCs cannot exceed 64.

*SAME: The existing PVC logical channel identifier values for this interface are used.

*NONE: All existing PVC logical channel identifier values for this interface are removed. If no PVC values are defined, *NONE is shown.

logical-channel-identifier: Specify the PVC logical channel identifier value. The value may be from 001 to FFF. Up to 64 PVC logical channel identifiers can be specified.

IDLVCTTIMO

Specifies the duration (in seconds) that the TCP/IP Network Access Manager (NAM) waits before clearing an idle virtual circuit established on an X.25 link. Clearing an idle virtual circuit frees resources on the network. TCP/IP automatically reestablishes virtual circuits when required to send or receive data. Virtual circuits are transparent to a TCP/IP client and have no noticeable effect on TCP connections.

Note:

This parameter is valid only for switched virtual circuits (SVCs) on an interface defined on an X.25 line description. It is not valid for permanent virtual circuits (PVCs).

*SAME: The existing idle virtual circuit timeout value for this interface is used.

number-of-seconds: Specify the idle virtual circuit timeout. Valid values range from 1 through 600 seconds.

MAXSVC

Specifies the maximum number of concurrent switched virtual circuits (SVC) that can be established on an X.25 interface by the TCP/IP protocol stack.

With this parameter you can share the line with other communications software, such as Systems Network Architecture (SNA). It prevents the TCP/IP protocol stack from monopolizing the SVCs defined for the line. This parameter is valid only for an interface defined on an X.25 line description.

Note:

The sum of the maximum switched virtual circuits (MAXSVC) and the number of PVCs cannot exceed 64.

*SAME: The existing maximum SVC value for this interface is used.

X.25-maximum-virtual-circuits: Specify the number of SVCs that the TCP/IP protocol stack can use simultaneously. The valid values range from 0 through 64. If 64 is specified, the number of SVCs that are configured is calculated by adding the number of *SVCIN, *SVCOUT and *SVCBOTH SVCs defined for the line description (LIND) being used by this interface. This is the maximum number of SVCs that can be authorized for processing by the TCP/IP protocol stack.

DDN

Specifies whether the X.25 interface is connected to the Defense Data Network. The DDN network is a special type of X.25 network used by TCP/IP customers with special security needs.

Note:

This parameter is valid only for switched virtual circuits (SVCs) on an interface defined on an X.25 line description. It is not valid for permanent virtual circuits (PVCs).

Attention:

If you specify multiple interfaces to the same X.25 network, the DDN value should be equal for all of those interfaces. This is not enforced by the ADDTCPIFC or CHGTCPIFC commands.

If the X.25 network is the DDN network, do not define the remote system information for any of the remote systems on the network. The remote system information for the DDN X.25 network is determined from the destination IP address.

*SAME: The existing DDN value for this interface is used.

*NO: The X.25 interface is not connected to the Defense Data Network.

*YES: The X.25 interface is connected to the Defense Data Network.

BITSEQ

Specifies the order, most or least significant bit first, in which the Address Resolution Protocol (ARP) places the bits in the hardware address. This parameter is valid only for a token-ring local area network (TRLAN) line.

Note:

All interfaces defined to a single token-ring line must have the same BITSEQ value. This is checked by the CHGTCPIFC code to ensure consistent values.

*SAME: The existing bit sequence value for this interface is used.

*MSB: The most significant bit is placed first.

*LSB: The least significant bit is placed first.

Examples for CHGTCPIFC

Example 1: Changing Autostart Value

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

This command assumes 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')
  INDLVCTTIMO(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.

Error messages for CHGTCPIFC

*ESCAPE Messages

TCP1D03

&1 member record length not correct.

TCP1D04

Error occurred processing member &1 of &2/&3.

TCP1901

Internet address &1 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.