Bug ID 781445: Named or dnscached cannot bind to IPv6 address

Last Modified: Sep 13, 2023

Affected Product(s):
BIG-IP APM(all modules)

Known Affected Versions:, 13.1.4,, 13.1.5,, 14.1.0,,,,,, 14.1.2, 15.0.0, 15.0.1,,,,

Fixed In:

Opened: May 10, 2019

Severity: 4-Minor


In some scenarios, the named process cannot bind to IPv6 addresses. This occurs because the dnscached process listens to the wildcard IPv6 address port 53 (i.e., :::53) so it cannot respond to queries sent to IPv6 addresses. Following message is reported in ltm log: err named[16593]: binding TCP socket: address in use.


The named process does not respond to the queries that are sent to IPv6 addresses at port 53.


-- The named and dnscached processes are not running. -- The dnscached process is started first. -- The named process is started later.


1) Stop both named and dnscached process. 2) Edit the startup script for dnscached to start in IPv4-only mode. 2a) On BIG-IP system, open the file /etc/bigstart/startup/dnscached. 2b) Add "-4" to the command line option of dnscached. That's done in "/etc/bigstart/scripts/dnscached" add "-4" so this line: exec /usr/sbin/dnscached -f -t $chroot_home -u named -c /config/named.conf -n 1 Now reads like this: exec /usr/sbin/dnscached -4 -f -t $chroot_home -u named -c /config/named.conf -n 1 3) Restart the processes: bigstart restart named dnscached

Fix Information

The dnscached startup script has been modified to start in IPv4-only mode, so it does not listen on any IPv6 address.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips