I‘m getting slow DNS response from ssh and other network related traffic with delay of 30-60+ seconds per connection. All of our servers are behind hardware based dedicated firewall. My RHEL v6.1 server system running on HP hardware. How do I fix this problem?
ADVERTISEMENTS
This is well known problem with RHEL 6 based systems and can be fixed by adding the following line to /etc/resolv.conf
options single-request-reopen
Save and close the file. This should fix the problem as the resolver uses the same socket for the A and AAAA requests. Turning this option on changes this behavior so that if two requests from the same port are not handled correctly it will close the socket and open a new one before sending the second request[1].
References:
- [1] This solution is documented RHN KB ID # 58626 (Red hat subscription required)
🐧 If you liked this page, please support my work on Patreon or with a donation.
🐧 Get the latest tutorials on SysAdmin, Linux/Unix, Open Source/DevOps topics:
🐧 Get the latest tutorials on SysAdmin, Linux/Unix, Open Source/DevOps topics:
- RSS feed or Weekly email newsletter
- Share on Twitter • Facebook • 1 comment... add one ↓
UP NEXT
CentOS / RHEL: Yum Lock Package Version At a Particular Version
Linux Configure Firewall Using Shorewall Under RHEL / CentOS
Linux Make Sure /etc/resolv.conf Never Get Updated By DHCP Client
HowTo: UNIX / Linux Open TCP / UDP Ports- How to set up a UFW firewall on Ubuntu 16.04 LTS server
CentOS / Redhat Iptables Firewall Configuration Tutorial
Bash Iterate Array Examples
| Category | List of Unix and Linux commands |
|---|---|
| File Management | cat |
| Firewall | Alpine Awall • CentOS 8 • OpenSUSE • RHEL 8 • Ubuntu 16.04 • Ubuntu 18.04 • Ubuntu 20.04 |
| Network Utilities | dig • host • ip • nmap |
| OpenVPN | CentOS 7 • CentOS 8 • Debian 10 • Debian 8/9 • Ubuntu 18.04 • Ubuntu 20.04 |
| Package Manager | apk • apt |
| Processes Management | bg • chroot • cron • disown • fg • jobs • killall • kill • pidof • pstree • pwdx • time |
| Searching | grep • whereis • which |
| User Information | groups • id • lastcomm • last • lid/libuser-lid • logname • members • users • whoami • who • w |
| WireGuard VPN | Alpine • CentOS 8 • Debian 10 • Firewall • Ubuntu 20.04 |
I ran into same issue and this is a very nice fix. Thanks. However, whenever I reboot the system, the line “options single-request-reopen” is gone from /etc/resolve.conf file.
I disabled selinux and removed the line “/etc/resolv.conf” from the file /etc/selinux/restorecond.conf. Still no luck. After rebooting, the change is reversed. Do you have any idea? Thanks again.