Re: Restricting ports/services to specific interfaces

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]

h
Hello Steve,

You wrote:
>Before you write the UIM book, please write one on configuring as400
>tcp/ip.

There are dozens of books on configuring TCP.  All you  need to know to use
one in relation to the AS/400 is how to translate the Unix-ish commands to
AS/400 commands.  Also, the TCP/IP Fast Path Setup and the TCP/IP
Configuration and Reference manuals do a pretty good job.

>On the subnet subject, I am interested in knowing about the cmds used to
>config, display and activate a subnet.

A subnet is nothing special.  It is basically as simple as different IP
ranges.  The IP range and the network mask operate together to define the
subnet. Here is one subnet: 192.168.0.nnn with a mask of 255.255.255.0.
Here is another subnet: 192.168.1.nnn with a mask of 255.255.255.0. Although
they may more properly be thought of as separate networks.

You can get clever and subnet within a range of addresses.  So with a
network mask of 255.255.255.128 I am indicating that the high-order bit of
the normal host address byte is actually the last part of the network
address.  Therefore a 192.168.0.nnn network is split into two networks
(because the high-order bit can be have only two states) with 126 host
addresses in each sub-network.

The addresses from 192.168.0.1 to 192.168.0.126 are in one network and
addresses from 192.168.0.129 to 192.168.0.254 are in the other network.  The
missing addresses are either not valid (all zeroes) or broadcast (all ones).
Note that it is more common to subnet class A and B networks rather than
class C as in this example.

ADDTCPIFC allows you to assign an IP address an mask to an interface.  If
multiple interfaces use an address in the same range with the same mask they
are in the same subnet.

ADDTCPRTE allows you to route between subnets.

NETSTAT *RTE shows you the routes and subnet masks accessibe from your
system.

Regards,
Simon Coulter.

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