CHGTCPRTE (Change TCP/IP Route) Command
Purpose
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
(*DFTROUTE and DFTMCAST), the NEXTHOP, TOS and BINDIFC values uniquely define
the route because the SUBNETMASK is always *NONE.
Restrictions:
1. You must have *IOSYSCFG special authority to use this command.
2. 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.
3. Attempts to change a route that is required to reach an existing RSI entry
will fail.
Required Parameters
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 system
allows a maximum of 8 default route entries. 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: Specifies that a default multicast route entry is being
changed. A default multicast route entry is used by the system to select a local
interface when sending data to a multicast group. The default multicast entry is
used when the application does not specifically name the local interface over
which multicast packets should be sent. When RTEDEST(*DFTMCAST) is specified,
SUBNETMASK(*NONE) must be specified and the NEXTHOP parameter must be the
internet address of an interface that had previously been added with the Add
TCP/IP Interface (ADDTCPIFC) command.
route-destination: 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.
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: There is no subnet mask. If RTEDEST(*DFTROUTE) or
RTEDEST(*DFTMCAST) is specified, SUBNETMASK(*NONE) must be specified. *NONE is
valid only for the *DFTROUTE and *DFTMCAST route destination values.
*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.
subnet-mask: 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.
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.
NEXTHOP Specifies the internet address of the next system
(gateway) on the route.
internet-address: 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.
BINDIFC The local IP interface to bind this route to. The binding
is preferred and not absolute.
If the IP interface defined for BINDIFC is active then the route specified
will be bound to that interface. If the IP interface defined for BINDIFC is not
active then another active IP interface using the same line description will be
used. If the IP interface defined for BINDIFC is not active and no other
interfaces using the same line description are active then any route and no
other interfaces using the same line description are active then any active
interface on the same network will be used. If no IP interfaces on the same
network are available then the route will be disabled.
*SAME: The specified interface will not be changed from its
current setting.
*NONE: TCP/IP will not attempt to bind this route to a particular
IP interface but will bind it to the first active IP interface on the network as
defined by the NEXTHOP and SUBNETMASK parameters.
binding interface: Specify an IP interface to bind this
route to. The binding is preferred and not absolute.
Optional Parameters
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.
maximum-transmission-unit: 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
Notes:
1. 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.
2. 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.
3. 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.
METRIC Specifies the cost associated with the use of this route. A
value of 1 is a route that is close (nearby), whereas a route with a value of 15
is relatively far away. A route with a Metric of 16 is considered to be
unreachable (infinitely far away).
*SAME: The value of the route metric will not change from its
current value.
metric-value: Specify a metric value. Valid metric values range
from 1 to 16.
REDST Specifies whether this statically-defined route is to be
redistributed (made available to other routers) in the future.
*SAME: The route redistribution value will not change from its
current setting.
*YES: Specifies that this route will be shown (redistributed) to
other routers. This is the default.
*NO: Specifies that this route will not be shown
(redistributed) to other routers.
Note: REDST(*YES) is analogous to the RIPv1 specification of STATIC.
REDST(*NO) is analogous to the RIPv1 specification of PASSIVE.
DUPRTEPTY The duplicate route priority value allows for ordering
of duplicate routes within an internal route table. It allows specification of
which particular duplicate route should be tried first in cases where a route
cannot establish a connection.
*SAME: The priority value will not change from its current value.
priority-value: Specify a priority value. Valid values are in the
range of 1 to 10.
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.
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