SLES 11 server generating a lot of traffic and responding sluggish - NTP Reflection
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Here is the syntax: restrict address[mask mask]
For example: If you want to restrict access from the 10.0.0.0/8 subnet you would add the following line:
restrict 10.0.0.0 255.0.0.0 noquery
If you want to completely harden
NTP, use the following lines: (This is
the recommended solution)
restrict -4 default kod nomodify
notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery
This will not affect Time Synchronization.
For example a LAN trace taken on the sluggish server might show a lot of NTP traffic with one or more remote clients sending NTP requests with code:
This will cause NTP on the server to send a lot of data back to the clients.
If this is done multiple times a second, from one or more devices, it can cause the NTP daemon to use excessive amounts up CPU cycles.
See Security issues with NTP at: http://www.cvedetails.com/vulnerability-list/vendor_id-2153/NTP.html
VUL-0: CVE-2013-5211 is the specific issue described above.
Using the restrict -4 default kod nomodify notrap nopeer noquery and restrict -6 default kod nomodify notrap nopeer noquery configuration options hardens NTP against other security issues mentioned at the link above.
There is a lot of information out there on these issues. Here are a few examples:
NTP version 4.2.7 addresses these issues but it is still marked as Development.
As of the creation of this document the latest "Stable" or "Production" code is being shipped.
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- Document ID:7014543
- Creation Date: 11-Feb-2014
- Modified Date:03-Mar-2020
- SUSE Linux Enterprise Server
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