TCP/IP Configuration and Management Manual

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SCF Reference

TCP/IP Configuration and Management Manual—427132-004

4-32

ALTER SUBNET Command

Since non-contiguous mask values are not supported, netmask values such as

0.255.255.0, 255.0.255.0, 0.0.255.0 are considered invalid.

IRDP

enables (ON) or disables (OFF) the ICMP Router Discovery Protocol on the

SUBNET interface. IRDP is a mechanism for locating default routers and is

specified in RFC 1256. IRDP must also be enabled on any local LAN routers. If

redundant routers are configured with route hold-down times and advertisement

intervals of approximately 30 seconds, IRDP can be used to provide a “black hole,”

or dead gateway, detection mechanism. The NonStop TCP/IP subsystem

implements IRDP using IP broadcasts rather than IP multicasts.

ADDALIAS ip-addr

allows the addition of the alias IP address to the SUBNET specified in the ALTER

SUBNET command. The IP alias feature allows a process to be known to the

Internet by different IP addresses. For a display example of an alias, see INFO

SUBNET Display Format on page 4-49.

DELETEALIAS

allows the deletion of alias IP addresses that have been added by the ADDALIAS

attribute.

MTU size

changes the interface MTU size on SNAP-type SUBNETs when configured on

token-ring adapters. The minimum value is 512 bytes. The maximum value is

65526 bytes or the maximum supported by the token-ring LAN. The default for 4

mega-bit LANs is 4464 and for 16 mega-bit LANs is 17792.

X25IDLETIME time

changes the idle timeout value on X.25 type SUBNETs used to timeout X.25

connections. The default value is 2 minutes. The range accepted is 0 to 5000

minutes. If the time value is set to zero, the X.25 connections do not time out.

Setting the time value to zero or to a value larger than the default may result in

limiting the number of devices that can use the SUBNET. so be careful when you

alter this value.

Example

The following command alters the subnet mask and IPADDRESS for the SUBNET

$ZTC0.#SN1:

1-> ALTER SUBNET $ZTC0.#SN1, IPADDRESS 120.1.1.12, &

1-> SUBNETMASK %hFFFF0000