What does " no more TCP clients: quota reached" in bind log mean ?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 5.X

    • bind-9.3.6-*
    • bind97-*

  • Red Hat Enterprise Linux 6.x

    • bind-9.7
    • bind-9.8

  • Red Hat Enterprise Linux 7.x

    • bind-9.9

  • Red Hat Enterprise Linux 8.x

    • bind-9.11

Issue

  • What does bind log " no more TCP clients: quota reached" mean ?

Seeing the following message in bind log file.

<TIME_STAMP> client: warning: client <IP>#<PORT>: no more TCP clients: quota reached
OR
<TIME_STAMP> client: warning: client @0x7xxx (no-peer): TCP client quota reached: quota reached

What does this mean ?

Resolution

  • basically , this message means that 'max simultaneous client TCP connections' reached limit of bind DNS server.
  • To increase , or define tcp-clients in your named.conf file.

For example;

named.conf

options {
...(SNIP)...
      tcp-clients <NUMBER_OF_MAX_CLIENT>;
};

Root Cause

  • This message means that "max simultaneous client TCP connections" reached limit of bind DNS server.
  • In bind 9.9 or older, the default value of tcp-clients is 100.
  • In bind 9.11 or later, the default value of tcp-clients is 150.
  • You can refer bind document (/usr/share/doc/bind-/arm/Bv9ARM) like below:
    tcp-clients: The maximum number of simultaneous client TCP connections that the server will accept.
    The default is 100.

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