Problems Connecting to FTP.STAC.NYSED.GOV

I.   Reverse DNS Look-up.

Perhaps the most common problem involved in connecting to our FTP site involves what’s called a "Reverse DNS Look-up". This problem will result in this error message:

Unable to connect to remote Host

Remote sites seeking to access SED's FTP servers must allow a reverse DNS look-up to their host using the host-name that their inquiry came in with. If the reverse DNS look-up that SED runs comes up with a host name that differs from the host name that was received on the inquiry, then SED's security SW will not allow the connection.

Following is a more detailed explanation from SED’s FTP technician:

When someone tries to make a connection to SED’s ftp site, SED’s ftp software does the following security check:

A DNS lookup of the client IP address is done and a hostname is returned. The ftp software then takes the returned hostname and does a reverse DNS lookup on it as a check against IP spoofing (For example IP address 11.222.33.444 may return a hostname of ' ip444.parkcounty.org'.). The returned hostname should map back to the original IP address (ip444.parkcounty.org'-> 11.222.33.444). If it doesn't, which it should, the ftp server software drops the connection because it appears, to the ftpserver, that someone is making an attempt to spoof the IP address.

So the problem, in a nutshell, is that:

For the ftp client IP address, after doing a DNS lookup (you can use the nslookup command in windows2000 or Unix) and getting a returned hostname, that hostname, after doing a reverse DNS lookup (you can do this with the nslookup command in window2000 or Unix) should return the original IP address you started with.

II.   Bind: Can't assign requested address.

Note: The following information about the "Bind: Can't Assign Requested Address" error message is from Microsoft's website.

Bind: Can't Assign Requested Address from ftp.exe Using Winsock Proxy

The information in this article applies to:

Microsoft Proxy Server 1.0

Microsoft Proxy Server 2.0

Microsoft Internet Security and Acceleration Server 2000

SYMPTOMS: When you use ftp.exe from either a Microsoft Windows NT Server or a Microsoft Windows 95 client while it is configured to use the Winsock Proxy, you may get the following error message:

Bind: Can't Assign Requested Address 

CAUSE: This can be caused by one of the following reasons:

The IP address of the external interface of the Proxy Server is in the Local Address Table (LAT).

-OR-

The Proxy Server has one network interface and only one IP address.

WORKAROUND: Remove any references to external IP addresses from the LAT on the Proxy Server.

MORE INFORMATION: If the IP address of an external interface on the Proxy Server is in the LAT, it is considered by the proxy client to be internal. Because the client computer does not have an interface with the same IP address as the external IP address of the Proxy Server, you get the above error message.

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Please contact Kurt Dano @ 518 486-2248 / kdano@mail.nysed.gov

or Joe Seeman @ 518 486-2357 / jseeman@mail.nysed.gov

if you need assistance resolving these problems.

Last Updated: June 3, 2009