FTP problem

Hi all,

 

 

I'm using BIGIP 9.1.2.

 

 

I'm experiencing strange behaviour on a FTP virtual Server. I've a lots of mobile devices hidden behing the same routable Internet IP (Provider's one) and connecting to the same virtual FTP server. I've noticed that a bug is occuring very frequently:

 

 

- the client establishs a passive connexion: STORE, LIST, etc

 

- After the transfert is terminated the server send a "226 Transfert ok"

 

- the client sends one ACK paquet (for the preceding 226) containing a new command: e.g TYPE I

 

 

At this moment I can see the ACK containing this TYPE I request on the wan interface of the bigip but on the LAN interface I only see a ACK paquet (SEQ/ACK is ok) but no payload. Then the BigIP starts resending the "226 Transfer OK" as if it hasn't received the ACK (TYPE I) and this completely desynchronize the connexion leading to a cut.

 

Any hint about this ?

 

Is there a way to have some low level debug traces on the bigip ?