Monday 28 November 2022

ftp passve mode issues

FTP passive mode not working

Some issues seen:

1 ftp inspect on ASA

2 sometimes the server transmits t he inside IP instead of public. Sometimes the FW's or the client are fixing this up but an old client might not and tries to connect to an inside IP.


https://www.ibm.com/support/pages/remote-ftp-client-doing-passive-mode-gets-internal-ip-address-returned-227-entering-passive-mode-message



Passive mode 

client connects to server on random source port  eg 55555  to destination port 21

connection goes back from server source port 21 to the destination port on client 55555


Active mode

they setup a data and a control connection on different ports


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