Which IP addresses (static) for internal communication between two computers?

[Thomas Gunnarsrud]

I have a system running WinXP (embedded) that will have two LAN ports. Port
1 connects to another computer and port 2 can be connected to any kind of
private or public network, or not connected to anything.

However, Port 1 and the other remote computer connects directly and static.
They will and shall only communicate with each other and nothing else. This
is the only communication point on this secondary computer. I want to be
100% sure that in any kind of situation, this connection will not have any
conflicts with what Port 2 might see.

Is the only possibility to reserve some public IP range and use this
internally for Port1 or is it some other reserved IP-range that I might use
in this case? Nothing can be installed on the computers by a customer. Any
reserved private network ranges will not do, like 10.x.x.x, 172.16.x.x,
192.168.x.x, as they might appear on network port 2. And also the APIPA
range is excluded.

Suggestions?

Thomas

 

[smlunatick]

How about 122.0.0.2 to 127.0.0.254? Only 127.0.0.1 is reserved for all/any
loop-back network connections.

 

[Paul Johnson]

I have a system running WinXP (embedded) that will have two LAN ports.
Port 1 connects to another computer and port 2 can be connected to any
kind of private or public network, or not connected to anything.

However, Port 1 and the other remote computer connects directly and
static. They will and shall only communicate with each other and nothing
else. This is the only communication point on this secondary computer. I
want to be 100% sure that in any kind of situation, this connection will
not have any conflicts with what Port 2 might see.

Is the only possibility to reserve some public IP range and use this
internally for Port1 or is it some other reserved IP-range that I might
use in this case? Nothing can be installed on the computers by a customer.
Any reserved private network ranges will not do, like 10.x.x.x,
172.16.x.x, 192.168.x.x, as they might appear on network port 2. And also
the APIPA range is excluded.

I would not use the same range as whatever your adjoining network has. IE,
if your ISP is using network 10, don't use network 10, use network 192.168
instead.

 

[smlunatick]

The original poster was stating that they would like to "pre-configure"
the embedded device network so that it can be plugged in to any PC with
any other network. So the network IP scheme may/will never be known
until the time the device is connected.

 

[Thomas Gunnarsrud]

The original poster was stating that they would like to "pre-configure"
the embedded device network so that it can be plugged in to any PC with
any other network. So the network IP scheme may/will never be known
until the time the device is connected.

Exactly, this is our main issue. By the way.. would it be possible for
instance to restrict the ip range for loopback in WinXP, and use some area
here..?

 

[smlunatick]

Every TCP/IP network aware controller card only use one loop-back
address of 127.0.0.1. This is part of the TCP/IP network protocol
specifications. Addresses 127.0.0.2 to 127.0.0.254 "can" be locally
routed. I have set up a locally 127.0.0.2 routed "mini" network
between a router and DSL PPPoE modem. I have yet to see this "range"
of IP addresses used as general IP addresses over the LANs or Internet.

 

[Paul Johnson]

Please do not quote in reverse order.
http://wiki.ursine.ca/Best_Online_Quoting_Practices

The original poster was stating that they would like to "pre-configure"
the embedded device network so that it can be plugged in to any PC with
any other network. So the network IP scheme may/will never be known
until the time the device is connected.

Then the correct answer is mu[1]. Configuration of nearby networks must be
taken into consideration when designing your own network; it's not
something you can pre-configure for without knowledge of the environment
it's going to be used in up front.

[1] http://wiki.ursine.ca/mu

 

[Paul Johnson]

Please do not quote in reverse order.
http://wiki.ursine.ca/Best_Online_Quoting_Practices

Every TCP/IP network aware controller card only use one loop-back
address of 127.0.0.1. This is part of the TCP/IP network protocol
specifications. Addresses 127.0.0.2 to 127.0.0.254 "can" be locally
routed. I have set up a locally 127.0.0.2 routed "mini" network
between a router and DSL PPPoE modem. I have yet to see this "range"
of IP addresses used as general IP addresses over the LANs or Internet.

This is bad practice. 127.0.0.0/8 is reserved and is supposed to be the
same as 127.0.0.1/32. The correct answer is to use one of the IANA
non-routable networks for your LAN, and not the same network as any
adjacent to yours.

IANA non-routable networks:

10.0.0.0/8 (that is, 10.*)
172.16.0.0/12 (that is, 172.16-31.*)
192.168.0.0/24 (that is, 192.168.*)

All other networks are either reserved for future use or assigned to other
uses and should never be used on your hosts unless you know you are
assigned to that network.