FTP Server sometimes blackholes 1

[SpaceMaker]

I have an FTP server setup at home. I can reach it from my office but not from all locations/paths. e.g., a friend of mine in NY can't reach it. I also can't get to it from my second DSL line. When it can't be reached it looks like a blackhole. What's strange is that I can always get to the router's internal FTP server when I enable it.

What could be the difference between the two servers that would be path dependent?

I am having similar problems with SSH and Remore Desktop.

 

[pansophic]

Many applications will do a Reverse DNS lookup when a device attempts to connect. If this is the case (it is with many FTP implementations and should be with all SSH implementations) then the connecting device has to wait for the Reverse DNS lookup to time out before they will get a prompt. This can take up to 4 minutes.

You can turn off Reverse DNS lookup for most applications, and that should solve your problem.


pansophic

 

[bcastner]

Your broadband connection may be at fault - on either end of the connection. There are MTU issues, and port issues. While written in a Linksys context, the issue is universal:

http://www.broadbandreports.com/forum/remark,1700907~root=equip,16~mode=flat

http://www.broadbandreports.com/forum/remark,1381832;root=equip,16;mode=flat

 

[SpaceMaker]

Thanks, bcastner.

This sounds promising and I'm looking into it. And thanks for the second link. It led me to solve another problem of getting the server to use something other than port 21. I completely forgot about the special relation wih the router.

Also, thanks to pansophic. I don't think this is the problem in this case but useful info to know.

FWIW: I'm only using the FTP server to illustrate the problem and test the path as I have an FTP server in the router. For some time, I had suspected that my ISP was killing the SYN packet to the FTP server but, since the router answers, they obviousy haven't.

I normally use SSH.