![]() ![]() ![]() Since the client is behind CGN, it's not possible (without some difficulty involving total control of both sides attempting such a connection) for the client to be reachable from outside. That's the probable reason the server returns 500 Illegal PORT command. Service Providers MUST filter such packets on ingress links. O packets with Shared Address Space source or destination addresses MUST NOT be forwarded across Service Provider boundaries. Service Providers MUST filter incoming advertisements regarding Shared Address Space. O routing information about Shared Address Space networks MUST NOT be propagated across Service Provider boundaries. This document requests the allocation of an IPv4 /10 address block to be used as Shared Address Space to accommodate the needs of Carrier-Grade NAT (CGN) devices. I noticed that the PORT command's address you're using is in the 100.64.0.0/10 network which is in RFC 6598: You stated that you can't use passive mode: that usually means the FTP's server side is behind a restrictive (local or on the network path) firewall which has no configuration to allow the FTP server to open temporary random listening ports corresponding to the output of the PASV command. But the difficulty is now reversed: that's the server's firewall side which must cope with the random port chosen by the server when transmitting the PASV command's answer containing the IP and port. The PASV command instead makes the client initiate connections twice to the server: one for command and one for every data transfer. The FTP protocol, written before today's concept of firewall existed is quite complex: while the client connects to the server for commands, for data transfers (including the output of the LIST command, but not the output of the PWD command which is directly in the command connection) in so-called active mode that is the server which initiates the connection (usually from port 20, to a random port chosen by the client).Īll this makes it difficult for "dumb" firewalls to let FTP work with the PORT command. If it is an issue on my end, what can I try to fix it? Is this likely to be an issue with my end (the client) or the FTPĢ. ![]() The question I therefore have is in two parts:ġ. This is the first time I've been required to use active mode when connecting. I can connect to a regular FTP server in passive mode without issue. I've also checked that there is nothing blocked in iptables. Likewise, I've verified that UFW is inactive from running: However, when enabling passive mode I am met with the following problem: Probably worth mentioning I can successfully run pwd and I can change directories with cd given I already know the name of two directories.įtp: setsockopt (ignored): Permission deniedįrom doing a lot of googling I saw a variety of suggestions such as enabling passive mode, and checking my firewall. Here is a screenshot of my terminal window: I can connect to the FTP server, however, when running it in debug mode by passing the -d flag to the ftp command, I am met with errors when attempting to list files. I have tried this with Filezilla by enabling active ftp and also via the command line. I need to connect to an FTP server where the connection needs to be in active mode. Thank you for putting up with this intermittent and apparently bizarre problem.I'm currently running Ubuntu 19:10 as my primary operating system. I'm still getting by, but occasionally get the urge to beat this dead horse some more. I can't see how this could possibly cause a problem, but might "instant" logins be associated with my SSD somehow? Like some sort of caching happening? (I don't believe in this association but I throw it out for you to trample.) Things worked fine on my old laptop but started failing with my new laptop which my son set up with an SSD. Something else has occurred to me (though this my be a red herring). When login is fast/instant file copying fails! If the login is sluggish, it almost always works! This seems really bizarre to me but it is very consistent! "Slow" is often accompanied with initial connection failure, timeout, then connection success. When I login to the server with WinSCP the login sometimes is very *fast* (almost instantaneous). However I've observed the following that seems to be consistent. ![]()
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