backup fails suddenly with Bad IP connecting.

[bsc-computer]

since 11.09.2023 backup from a customer fails.
The backup is carried out via FTP.
Many other customers also successfully write the 3CX backups to the same FTP server.
FTP server can be reached via ping from 3CX Server Terminal.
Version 18.8. Build 935

message is:
Your 3CX backup failed due to the following reason(s): FluentFTP.Exceptions.FtpCommandException: Code: 425 Message: Security: Bad IP connecting. at FluentFTP.FtpClient.OpenPassiveDataStream(FtpDataConnectionType type, String command, Int64 restart) at FluentFTP.FtpClient.OpenDataStream(String command, Int64 restart) at FluentFTP.FtpClient.OpenWrite(String path, FtpDataType type, Int64 fileLen) at FluentFTP.FtpClient.OpenWrite(String path, FtpDataType type, Boolean checkIfFileExists) at _3cxFilesystemImplementations.FTP.FtpFilesystem.CreateFile(String filename) at _3cxBackupRestoreImpl.BackupRestoreUtils.Backup(IFilesystem filesystem, String instanceId, String cfgPath, IDbOperationAsync db, BackupConfig options, String fullpathFilename, Boolean sendEmail) at BackupRestoreSchedule.BackupJob.Execute(IJobExecutionContext context)


Any ideas what the problem?

 

[AWS2P]

Are you full IPV6 each ends ?
for those which works are they IPV4 ? V6 ?

no change on network settings? firewall rules?

Do you have multi Wan and may be load balancing changing IP source ?

on Google with this in search bar :Code: 425 Message: Security: Bad IP connecting.
There are things to test

 

[bsc-computer]

no IPV6 only IPV4
telephone system is untouched.
firewall I have to ask. is not within our control.

 

[AWS2P]

What is your FTP server?
Where is located your FTP server? in a datacenter ? do you manage the FW rules for incoming connections?
Do you have 3CX failover PBX ?

Are you sure nothing flip to IPV6 and then lose connection?

 

[bsc-computer]

>What is your FTP server?
vsftp
I have seen the link too
https://serverfault.com/questions/1...n-trying-to-connect-to-ftp-server-behind-load

>Where is located your FTP server?
datacenter

>do you manage the FW rules for incoming connections?
not at customer site

>Do you have 3CX failover PBX ?
No..

I next ask the client's admin if there has been any change since 11.09.2023.
Then I give feedback.

 

[AWS2P]

see there if your config file needs some adds
https://www.linuxquestions.org/ques...m-with-425-security-bad-ip-connecting-120158/

 

[bsc-computer]

The issue is not related to 3CX.
The solution has been found and was indeed related to our FTP server.
The error occurred only for customers who have multiple internet connections on their firewall, and NAT does not correctly separated the lines.

From the perspective of the FTP server (VSFTP), the error occurs because:
The FTP service has two connections, one is a control connection, and the other is a data connection. By default, the FTP server checks whether the source IP addresses of two connections are the same during data transmission. If they are not, a "425 Security:Bad IP connection" error is reported. This issue is often caused by the clients in the NAT network, and the public IP address associated with the NAT is more than one, resulting in two connections, the source IP is inconsistent.

edit the fle /etc/vsftpd/vsftpd.conf
and add the following content to the configuration file.
pasv_promiscuous=yes

After restart service FTP Backup works fine with.