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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 12, 2025

Hi... definitely not.  It's a new service with no iRules, no connection rate limit (setted at 0) and I think no SYN flood protection (it's a standard configuration, non customization). No OneConnect. Applied profiles are fastl4 standard and http profile standard. VS is on 61616 port. No connection exceeded rate limt logs.

I have really no ideas :-(

VGF5's avatar
VGF5
Icon for Cumulonimbus rankCumulonimbus
Jun 12, 2025

Are you using SNAT automap ? If not, try enabling SNAT automap on the VS and retest.
And also check the connection count per-TMM using the following article

K09047561: Viewing the current number of TMM connections from the BIG-IP command line

If this not helps, I would recommend you to open a support ticket to check further.

 

 

 

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

    yes, I have automap. 

    I'll try to check the connection count per-TMM and I setted a higher value at Default Per Virtual Server SYN Check threshold under System >> Configuration >> Local Traffic: General

      • 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....