Hi all,
I use the DNS server in my Mikrotik router RB850Gx2 (6.39). I’m running into the following issues, where a lookup can take at least 5 seconds to resolve from the DNS:
https://www.netroby.com/view/3695
http://blog.oracle48.nl/wordpress/tnsping-and-others-take-at-least-5-seconds-or-longer/
It’s fixed when I add one or both of the following lines in my /etc/resolv.conf :
options single-request
options single-request-reopen
It might be one or both of the following cases, as adding the options solve the issue:
- By default, glibc performs IPv4 and IPv6 lookups in parallel since version 2.9. Some appliance DNS servers cannot handle these queries properly and make the requests time out.
- The resolver uses the same socket for the A and AAAA requests. Some hardware mistakenly sends back only one reply. When that happens the client system will sit and wait for the second reply.
(taken from the man page http://man7.org/linux/man-pages/man5/resolv.conf.5.html)
Might it be possible the DNS server is not handling the parallel requests correctly and/or only returns one response?
Regards,
Airell.