Forum Discussion

DR2016_253175's avatar
DR2016_253175
Icon for Nimbostratus rankNimbostratus
Mar 07, 2016

Maximum number of TCP connections to LTM - is there a limit?

Hello, I am wondering if there is any system level restriction on the maximum number of TCP connections that can be opened to an LTM version 10.2.4 and 11.5.2. Is the limit determined by the system memory or are there any other constraints?

 

BIG-IP
connection limit
LTM
security
tcp
  • Hannes_Rapp's avatar
    Hannes_Rapp
    Icon for Nimbostratus rankNimbostratus
    Mar 08, 2016

    Yes, the platform itself/available memory determines the max number of records that can be held in the connection table. F5 has the estimate limits available in hardware datasheets.

    There's another TCP/IP protocol-related limitation that you should consider if you explicitly translate client source IP addresses (Source NAT), before the requests are routed to BigIP.

    The TCP/IP protocol has a limitation of 64k unique sessions 

    from a single IP client (i.e. 1.1.1.1), to the same Server IP/Port listener (i.e 2.2.2.2:443)
    . There's a dedicated 64k-unit-size range for TCP source ports that can be used by the client.

  • anthonymaw_com_'s avatar
    anthonymaw_com_
    Icon for Nimbostratus rankNimbostratus
    Dec 20, 2018

    We were doing web site performance capacity testing using a virtual server on a f5 Big-IP 1600 with 2 node back end, SSL pass through, round-robin algorithm, auto SNAT, using synthetic load generator. The default "Connection Limit" values for the virtual server, pool and nodes were found to be 0 but that appears to be a default connection limit of 200 before the software load generator reported dropped connection attempts so the default 0 value definitely not mean unlimited. Your results with other hardware models may vary.