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Forum Discussion

romolo82's avatar
romolo82
Icon for Cirrus rankCirrus
Jun 12, 2025

Issue on connection limit

Hi, we are having an issue with a VS on F5 LTM: when a client simulates a call to a service via the VS on F5 with simultaneous connections, the connections are blocked at a number of 28, whatever th...
application delivery
romolo82's avatar
romolo82
Icon for Cirrus rankCirrus
Jun 13, 2025

Hi, thanks a lot. I have this output:

rluciani01@(LTM-D-SERVIZI-01-D-01)(cfg-sync In Sync)(Active)(/Common)(tmos)# show /sys tmm-traffic

-------------------------------------------------
Sys::TMM: 0.0            
-------------------------------------------------
TMM Traffic                ClientSide  ServerSide
  Bits In                        2.4T        2.4T
  Bits Out                     487.2G      483.8G
  Packets In                     1.1G        1.1G
  Packets Out                   70.3M       69.8M
  Current Connections              10          10
  Maximum Connections              87          87
  Evicted Connections               0           0
  Slow Connections Killed           0           0
  Total Connections             20.1M       18.9M
  Total Requests                 1.2K           -
                         
Errors                   
  Maintenance Mode                  0
  Virtual Addr Limit                0
  Virtual Server Limit              0
  Wrong Address                     0
  No handler                   280.9K
  No Staged Handler                 0
  No license                        0
  Connection Memory                 0
  Packets Dropped                   0
  Packets In Errors                 0
  Packets Out Errors                0
Connections Redirected              0

-------------------------------------------------
Sys::TMM: 0.2            
-------------------------------------------------
TMM Traffic                ClientSide  ServerSide
  Bits In                      665.4G      663.8G
  Bits Out                     692.5G      690.5G
  Packets In                   313.5M      312.1M
  Packets Out                  135.4M      134.9M
  Current Connections               9           9
  Maximum Connections              90          90
  Evicted Connections               0           0
  Slow Connections Killed           0           0
  Total Connections             27.0M       25.8M
  Total Requests                 1.2K           -
                         
Errors                   
  Maintenance Mode                  0
  Virtual Addr Limit                0
  Virtual Server Limit              0
  Wrong Address                     0
  No handler                   281.1K
  No Staged Handler                 0
  No license                        0
  Connection Memory                 0
  Packets Dropped                   0
  Packets In Errors                 0
  Packets Out Errors                0
Connections Redirected              0


[rluciani01@LTM-D-SERVIZI-01-D-01:Active:In Sync] ~ # tmctl tmm_stat -s slot_id,cpu,client_side_traffic.cur_conns,server_side_traffic.cur_conns
slot_id cpu client_side_traffic.cur_conns server_side_traffic.cur_conns
------- --- ----------------------------- -----------------------------
      0   0                            10                            10
      0   2                             7                             7

[rluciani01@LTM-D-SERVIZI-01-D-01:Active:In Sync] ~ # tmctl tmm_stat -s slot_id,cpu,client_side_traffic.cur_conns,server_side_traffic.cur_conns
slot_id cpu client_side_traffic.cur_conns server_side_traffic.cur_conns
------- --- ----------------------------- -----------------------------
      0   0                             9                             9
      0   2                            11                            11

[rluciani01@LTM-D-SERVIZI-01-D-01:Active:In Sync] ~ # tmctl tmm_stat -s slot_id,cpu,client_side_traffic.cur_conns,server_side_traffic.cur_conns
slot_id cpu client_side_traffic.cur_conns server_side_traffic.cur_conns
------- --- ----------------------------- -----------------------------
      0   0                            10                            10
      0   2                             9                             9

[rluciani01@LTM-D-SERVIZI-01-D-01:Active:In Sync] ~ # tmctl tmm_stat -s slot_id,cpu,client_side_traffic.cur_conns,server_side_traffic.cur_conns
slot_id cpu client_side_traffic.cur_conns server_side_traffic.cur_conns
------- --- ----------------------------- -----------------------------
      0   0                            10                            10
      0   2                            12                            12

[rluciani01@LTM-D-SERVIZI-01-D-01:Active:In Sync] ~ # tmctl tmm_stat -s slot_id,cpu,client_side_traffic.cur_conns,server_side_traffic.cur_conns
slot_id cpu client_side_traffic.cur_conns server_side_traffic.cur_conns
------- --- ----------------------------- -----------------------------
      0   0                             9                             9
      0   2                            10                            10


These output are rilevated during simulated calls, but client side always same errors....

VGF5's avatar
VGF5
Icon for Cumulonimbus rankCumulonimbus
Jun 13, 2025

Thank you for the output. F5 is not enforcing a connection cap, and the system is healthy. The next step is to check for external, server-side, or network path limits, and to use packet capture to see where the connection is being refused or dropped.

tcpdump -ni 0.0:nnnp port 61616 -s0 -w /var/tmp/port61616_test.pcap