Forum Discussion

Nimbostratus

Nov 04, 2019

Slow FTP connection behind F5

Hello there, I have an issue I don't understand. Some customers connect on one of our FTP server behind the F5. Public IP of the virtual server on port 21 > default pool > one server por...

application delivery

BIG-IP

Vijay_E

Cirrus

Nov 18, 2019

Tough to answer without seeing the packet capture. Are you seeing still seeing the same issue directly to the server and via F5 ? Try disabling Nagle's algorithm on F5 (or server) and see if it makes any difference.

Network_center1
Nimbostratus
Nov 18, 2019
The issue is only via F5 ^^

I opened your link and don't understand much '^^
- PeteWhite
  Employee
  Nov 18, 2019
  Take a tcpdump to see where the issue is, there is no point guessing. Then you can define the problem better and target your investigation. I mentioned DNS before because the server often uses DNS to resolve the name of the incoming IP address. If it can’t do that eg SNAT then it can cause a delay on the server
- Network_center1
  Nimbostratus
  Nov 19, 2019
  Did the tcpdump on the lan side, nothing to see here.
  
  F5 > ftp request : USER usertest
  ftp > F5 ACK
  ****
  5second blank
  ****
  ftp > F5 response : 331 password required for usetest
  F5 > ftp ACK
  
  The same when the password is sent, and when the directory is required.
- boneyard
  MVP
  Nov 30, 2019
  it would be useful to check both sides, is there anything coming from the FTP server which the BIG-IP doesn't pass through or does the BIG-IP wait on sending something.
  
  this is way easier to trouble shoot for f5 support, if you haven't already open a support ticket.