Change TCP/IP Route (CHGTCPRTE)

The Change TCP/IP Route (CHGTCPRTE) command is used to change an existing route in the Transmission Control Protocol/Internet Protocol (TCP/IP) configuration.

Five parameter values uniquely define a route. These values are the route destination (RTEDEST) the subnet mask (SUBNETMASK), the type of service (TOS), the internet address of the next system on the route (NEXTHOP), and the preferred binding interface (BINDIFC). For default routes and default multicast routes (*DFROUTE and *DFTMCAST), the NEXTHOP, TOS and BINDIFC values uniquely define the route because the SUBNETMASK is always *NONE.

Restrictions:

You must have input/output system configuration (*IOSYSCFG) special authority to run this command.
Only one parameter, the MTU value, can be changed on an existing route entry. The route cannot be in use when attempting to change its MTU value.
Attempts to change a route that is required to reach an existing RSI entry will fail.

Parameters

Keyword	Description	Choices	Notes
RTEDEST	Route destination	Character value, DFTROUTE, DFTMCAST	Required, Key, Positional 1
SUBNETMASK	Subnet mask	Character value, NONE, HOST	Required, Key, Positional 2
TOS	Type of service	MINDELAY, MAXTHRPUT, MAXRLB, MINCOST, *NORMAL	Optional, Key, Positional 3
NEXTHOP	Next hop	Character value	Optional, Key
BINDIFC	Preferred binding interface	Character value, *NONE	Optional, Key
MTU	Maximum transmission unit	576-16388, SAME, IFC	Optional
METRIC	Route metric	1-16, *SAME	Optional
REDST	Route redistribution	SAME, YES, *NO	Optional
DUPRTEPTY	Duplicate route priority	1-10, *SAME	Optional

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Route destination (RTEDEST)

Specifies the route destination being changed. You must specify all 4 bytes that make up an internet address though some of the bytes may be equal to 0. For example, a route to all the hosts on the 9.5.11 subnetwork is identified by entering 9.5.11.0 for the route destination. Used in combination with a subnetmask, type of service value, and next hop, the route destination uniquely identifies a route to a network or system.

*DFTROUTE

Specifies that a default route entry is being changed. A default route entry is used by the system to route data that is being sent to a remote destination that does not have a specific route defined. The default route entries are used based on the availability of the next hop gateway and the type of service (TOS). If the application requests a specific TOS, the TOS of the default route used must match the TOS requested. If no default route is found that matches the requested TOS, the first available default route with a TOS of *NORMAL is used.

*DFTMCAST

Use the *DFTMCAST special value to indicate that the static route you are changing is a default Multicast route. The default Multicast route is used by an application when no specific route is specified.

Note: When RTEDEST(*DFTMCAST) is specified, then SUBNETMASK(*NONE) must also be specified and the NEXTHOP parameter must be a local TCP/IP interface (on this system).

character-value

Specify the route destination being changed. The route destination can be specified in the form nnn.0.0.0, for Class A, nnn.nnn.0.0 for Class B, and nnn.nnn.nnn.0 for Class C, or nnn.nnn.nnn.nnn for any combination thereof, where nnn is a decimal number ranging from 0 through 255.

Any combination thereof means that you may specify a route, such as 9.5.0.0 to the hosts on the 9.5 subnet, even though all 9.5.x.x addresses are class A network addresses.

Exceptions:

The first byte (octet) must be greater than 0 and less than 255.
The last byte (octet) may not equal 255.
The last byte (octet) may not equal 0 if *HOST is specified for the SUBNETMASK value.
Routes to a broadcast address are not allowed.

Subnet mask (SUBNETMASK)

Specifies a bit mask that identifies to TCP/IP which bits of the value specified for the route destination (RTEDEST) compose the network and subnet portions of the internet address. By defining the network portion and subnetwork portion of the RTEDEST address, the subnet mask also defines which bits of the RTEDEST address make up the host portion.

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.

*NONE: No subnet mask is used. A subnet mask is not used when specifying default routes. For example, when RTEDEST(*DFTMCAST) or RTEDEST(*DFTROUTE) is specified, SUBNETMASK(*NONE) must also be specified.
*HOST: The internet address value specified in the route destination field is a host address. The subnetmask value is calculated to be 255.255.255.255.
character-value: Specify the mask of the subnet field. The internet address is in the form nnn.nnn.nnn.nnn, where nnn is a decimal number ranging from 0 through 255. For example, a destination route's internet address value of 129.35.11.0 is a Class B subnet. The network ID part of its address is 129.35. The upper 2 bytes must designate 255 in the subnetmask. The subnetmask must appear like 255.255.x.x, where x is determined by the user. The portion of the subnetmask that is associated with the network portion of a particular class of address must equal 255.

Type of service (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.

*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.

Next hop (NEXTHOP)

Specifies the internet address of the next system (gateway) on the route.

character-value: Specify the internet address of the next system on the route. 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.

Preferred binding interface (BINDIFC)

Specifies the IP interface this route will be bound to. The bind is absolute.

Note: This parameter is useful only when there are multiple interfaces defined on your system for the same network. BINDIFC allows you to define which interface should be used to reach the network for a particular route destination. In this way you can distribute traffic (load balancing) across multiple interfaces so all routes do not use the same interface to reach the network.

If the IP interface you specify is active, this route will bind to it, otherwise it will follow the normal route binding rules (which are also used when BINDIFC is defined as *NONE).

*NONE: No particular IP interface will be bound to this route. The first active IP interface on the network defined by the NEXTHOP and SUBNETMASK parameters will be used. This is the default value.
character-value: Enter the internet address (IP address) of the interface you want this route to bind to.

Maximum transmission unit (MTU)

Specifies the maximum size (in bytes) of IP datagrams that can be transmitted through this route. 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.

*SAME

The existing maximum transmission unit value for this route is used.

*IFC

The maximum transmission unit (MTU) is the MTU of the interface that is associated with this route.

576-16388

Specify a value for the maximum transmission unit in bytes. The maximum MTU that can be specified for this route 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:

TCP/IP uses the route MTU value to calculate the size of the datagrams it sends. For best performance, specify a value that is no smaller than the smallest MTU used by host systems along the entire path of this route. If this information is not available, use the default value of 576.
The MTU of a route cannot exceed the MTU of the interface on which the NEXTHOP value is accessed. If the interface's MTU value was specified as *LIND, the interface's MTU value is derived from the line description. If the route's MTU value is specified as *IFC and the interface's MTU value is specified as *LIND, both values are derived from the line description.
The actual MTU value used for a route is resolved during interface activation. This value is the minimum of either the specified MTU value for the route or the MTU value determined from the associated interface used by the route.

Route metric (METRIC)

Allows you to assign a routing metric "cost" value to this route. The metric cost of a route is a factor in determining the desirability of the route. The metric value range is from 1 to 16. A metric value of 1 is close (one router hop) and therefore desirable. Desirability decreases as the metric value (distance) increases. A metric value of 16 is considered unreachable (an infinite distance away).

You can discourage the routing table from choosing this route by specifying a metric value that is higher than the actual number of hops to the destination and therefore reduce traffic on this route.

*SAME: The value of the route metric will not change from its current value.
1-16: Specify a metric value.

Route redistribution (REDST)

Specifies whether this static route information will be shared with other routers. You can reduce traffic on this route by specifying *NO.

*SAME: The route distribution value will not change from its current setting.
*YES: *YES means that this route will be shown to any requesting router.
NO: *NO means this route will not be shown or shared with other routers.

Note: REDST(*YES) is analogous to the RIPv1 specification of STATIC. REDST(*NO) is analogours to the RIPv1 SPECIFICATION OF passive.

Examples

Example 1: Changing a Route

CHGTCPRTE   RTEDEST('132.65.0.0')  SUBNETMASK('255.255.0.0')
            TOS(*MINDELAY) NEXTHOP('132.65.34.98')  MTU(1024)

This command changes the route identified by route destination 132.65.0.0 with a subnetmask of 255.255.0.0 and type of service of *MINDELAY. The change is to use a maximum transmission unit (MTU) of 1024.

Example 2: Changing a Default Route

CHGTCPRTE   RTEDEST(*DFTROUTE)  SUBNETMASK(*NONE)  TOS(*NORMAL)
            NEXTHOP('186.49.126.108')  MTU(1024)

This command changes the default route identified by next-hop value 186.49.126.108 to use an MTU value of 1024.

Error messages

*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.
TCP261C: Process completed successfully.
TCP2658: &2 &1 not changed.
TCP8050: *IOSYSCFG authority required to use &1.
TCP9509: Line &1 not found.
TCP9999: Internal system error in program &1.