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Submit A Design
FTP Failed, Private Host Error
Text of Error Message
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Host specification (n.n.n.n) designates a private host to which
we cannot connect.
The Host specification is not valid for ftp (see appended text for
detail).
How To Correct
Fill out the fabricate web form completely except for the IP address
of the FTP-SEND-HOST. From your computer, ftp to ftp.design.mosis.com
and note the reported IP address of your computer. Go back to the
fabricate web form and enter this IP address in the fabricate web form
and submit. Continue using the ftp connection previously opened.
Background on the issue:
Certain ranges of IP addresses are reserved for private internets.
These IP addresses are not globally unique - that is,
many computers in different companies could have the same IP address.
These IP addresses therefore have no routing information, since they
don't represent a unique host.
The following is an exerpt from the online document, "RFC 1918 -
Address Allocation for Private Internets." See
RFC 1918 for more
information and the complete text.
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"3. Private Address Space
"The Internet Assigned Numbers Authority (IANA) has reserved the
following three blocks of the IP address space for private internets:
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10.0.0.0
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10.255.255.255
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(10/8 prefix)
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172.16.0.0
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172.31.255.255
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(172.16/12 prefix)
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92.168.0.0
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192.168.255.255
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(192.168/16 prefix)
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"We will refer to the first block as '24-bit block', the second as
'20-bit block', and to the third as '16-bit' block. Note that (in
pre-CIDR notation) the first block is nothing but a single class A
network number, while the second block is a set of 16 contiguous class
B network numbers, and third block is a set of 256 contiguous class C
network numbers.
"An enterprise that decides to use IP addresses out of the address
space defined in this document can do so without any coordination with
IANA or an Internet registry. The address space can thus be used by
many enterprises. Addresses within this private address space will
only be unique within the enterprise, or the set of enterprises which
choose to cooperate over this space so they may communicate with each
other in their own private internet.
"As before, any enterprise that needs globally unique address space is
required to obtain such addresses from an Internet registry. An
enterprise that requests IP addresses for its external connectivity
will never be assigned addresses from the blocks defined above.
"In order to use private address space, an enterprise needs to
determine which hosts do not need to have network layer connectivity
outside the enterprise in the foreseeable future and thus could be
classified as private. Such hosts will use the private address space
defined above. Private hosts can communicate with all other hosts
inside the enterprise, both public and private. However, they cannot
have IP connectivity to any host outside of the enterprise. While not
having external (outside of the enterprise) IP connectivity private
hosts can still have access to external services via mediating
gateways (e.g., application layer gateways).
"All other hosts will be public and will use globally unique address
space assigned by an Internet Registry. Public hosts can communicate
with other hosts inside the enterprise both public and private and can
have IP connectivity to public hosts outside the enterprise. Public
hosts do not have connectivity to private hosts of other enterprises.
"Moving a host from private to public or vice versa involves a change
of IP address, changes to the appropriate DNS entries, and changes to
configuration files on other hosts that reference the host by IP
address.
"Because private addresses have no global meaning, routing information
about private networks shall not be propagated on inter-enterprise
links, and packets with private source or destination addresses should
not be forwarded across such links. Routers in networks not using
private address space, especially those of Internet service providers,
are expected to be configured to reject (filter out) routing
information about private networks. If such a router receives such
information the rejection shall not be treated as a routing protocol
error.
"Indirect references to such addresses should be contained within the
enterprise. Prominent examples of such references are DNS Resource
Records and other information referring to internal private
addresses. In particular, Internet service providers should take
measures to prevent such leakage.
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"4. Advantages and Disadvantages of Using Private Address Space
"The obvious advantage of using private address space for the Internet
at large is to conserve the globally unique address space by not using
it where global uniqueness is not required.
"Enterprises themselves also enjoy a number of benefits from their
usage of private address space: They gain a lot of flexibility in
network design by having more address space at their disposal than
they could obtain from the globally unique pool. This enables
operationally and administratively convenient addressing schemes as
well as easier growth paths.
"For a variety of reasons the Internet has already encountered
situations where an enterprise that has not been connected to the
Internet had used IP address space for its hosts without getting this
space assigned from the IANA. In some cases this address space had
been already assigned to other enterprises. If such an enterprise
would later connects to the Internet, this could potentially create
very serious problems, as IP routing cannot provide correct operations
in presence of ambiguous addressing. Although in principle Internet
Service Providers should guard against such mistakes through the use
of route filters, this does not always happen in practice. Using
private address space provides a safe choice for such enterprises,
avoiding clashes once outside connectivity is needed.
"A major drawback to the use of private address space is that it may
actually reduce an enterprise's flexibility to access the Internet.
Once one commits to using a private address, one is committing to
renumber part or all of an enterprise, should one decide to provide IP
connectivity between that part (or all of the enterprise) and the
Internet. Usually the cost of renumbering can be measured by counting
the number of hosts that have to transition from private to public. As
was discussed earlier, however, even if a network uses globally unique
addresses, it may still have to renumber in order to acquire
Internet-wide IP connectivity.
"Another drawback to the use of private address space is that it may
require renumbering when merging several private internets into a
single private internet. If we review the examples we list in Section
2, we note that companies tend to merge. If such companies prior to
the merge maintained their uncoordinated internets using private
address space, then if after the merge these private internets would
be combined into a single private internet, some addresses within the
combined private internet may not be unique. As a result, hosts with
these addresses would need to be renumbered.
"The cost of renumbering may well be mitigated by development and
deployment of tools that facilitate renumbering (e.g. Dynamic Host
Configuration Protocol (DHCP)). When deciding whether to use private
addresses, we recommend to inquire computer and software vendors about
availability of such tools. A separate IETF effort (PIER Working
Group) is pursuing full documentation of the requirements and
procedures for renumbering."
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