Network Time Protocol - NTP
The ntpd
daemon running on the switch implements the NTP protocol. It synchronizes the system time with time servers in the /etc/ntp.conf
file. The ntpd
daemon starts at boot by default.
If you intend to run this service within a VRF, including the management VRF, follow these steps to configure the service.
Configure NTP Servers
The default NTP configuration includes the following servers, which are in the /etc/ntp.conf
file:
- server 0.cumulusnetworks.pool.ntp.org iburst
- server 1.cumulusnetworks.pool.ntp.org iburst
- server 2.cumulusnetworks.pool.ntp.org iburst
- server 3.cumulusnetworks.pool.ntp.org iburst
To add the NTP servers you want to use, run the following commands. Include the iburst
option to increase the sync speed.
The NVUE command requires a VRF. The following command adds the NTP servers in the default VRF.
cumulus@switch:~$ nv set service ntp default server 4.cumulusnetworks.pool.ntp.org iburst on
cumulus@switch:~$ nv config apply
Edit the /etc/ntp.conf
file to add or update NTP server information:
cumulus@switch:~$ sudo nano /etc/ntp.conf
# pool.ntp.org maps to about 1000 low-stratum NTP servers. Your server will
# pick a different set every time it starts up. Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
server 0.cumulusnetworks.pool.ntp.org iburst
server 1.cumulusnetworks.pool.ntp.org iburst
server 2.cumulusnetworks.pool.ntp.org iburst
server 3.cumulusnetworks.pool.ntp.org iburst
server 4.cumulusnetworks.pool.ntp.org iburst
To set the initial date and time with NTP before starting the ntpd
daemon, run the ntpd -q
command. Be aware that ntpd -q
can hang if the time servers are not reachable.
To verify that ntpd
is running on the system:
cumulus@switch:~$ ps -ef | grep ntp
ntp 4074 1 0 Jun20 ? 00:00:33 /usr/sbin/ntpd -p /var/run/ntpd.pid -g -u 101:102
To check the NTP peer status:
cumulus@switch:~$ nv show service ntp default server
cumulus@switch:~$ ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
+ec2-34-225-6-20 129.6.15.30 2 u 73 1024 377 70.414 -2.414 4.110
+lax1.m-d.net 132.163.96.1 2 u 69 1024 377 11.676 0.155 2.736
*69.195.159.158 199.102.46.72 2 u 133 1024 377 48.047 -0.457 1.856
-2.time.dbsinet. 198.60.22.240 2 u 1057 1024 377 63.973 2.182 2.692
The following example commands remove some of the default NTP servers:
cumulus@switch:~$ nv unset service ntp default server 0.cumulusnetworks.pool.ntp.org
cumulus@switch:~$ nv unset service ntp default server 1.cumulusnetworks.pool.ntp.org
cumulus@switch:~$ nv unset service ntp default server 2.cumulusnetworks.pool.ntp.org
cumulus@switch:~$ nv unset service ntp default server 3.cumulusnetworks.pool.ntp.org
cumulus@switch:~$ nv config apply
Edit the /etc/ntp.conf
file to delete NTP servers.
cumulus@switch:~$ sudo nano /etc/ntp.conf
...
# pool.ntp.org maps to about 1000 low-stratum NTP servers. Your server will
# pick a different set every time it starts up. Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
server 4.cumulusnetworks.pool.ntp.org iburst
...
Specify the NTP Source Interface
By default, the source interface that NTP uses is eth0. The following example command configures the NTP source interface to be swp10.
cumulus@switch:~$ nv set service ntp default listen swp10
cumulus@switch:~$ nv config apply
Edit the /etc/ntp.conf
file and modify the entry under the Specify interfaces
comment.
cumulus@switch:~$ sudo nano /etc/ntp.conf
...
# Specify interfaces
interface listen swp10
...
Use NTP in a DHCP Environment
You can use DHCP to specify your NTP servers. Ensure that the DHCP-generated configuration file /run/ntp.conf.dhcp
exists. The /etc/dhcp/dhclient-exit-hooks.d/ntp
script generates this file, which is a copy of the default /etc/ntp.conf
file with a modified server list from the DHCP server. If this file does not exist and you plan on using DHCP in the future, you can copy your current /etc/ntp.conf
file to the location of the DHCP file.
To use DHCP to specify your NTP servers, run the sudo -E systemctl edit ntp.service
command and add the ExecStart=
line:
cumulus@switch:~$ sudo -E systemctl edit ntp.service
[Service]
ExecStart=
ExecStart=/usr/sbin/ntpd -n -u ntp:ntp -g -c /run/ntp.conf.dhcp
The sudo -E systemctl edit ntp.service
command always updates the base ntp.service
even if you use ntp@mgmt.service
. The ntp@mgmt.service
is re-generated automatically.
To validate that your configuration, run these commands:
cumulus@switch:~$ sudo systemctl restart ntp
cumulus@switch:~$ sudo systemctl status -n0 ntp.service
If the state is not Active, or the alternate configuration file does not appear in the ntp
command line, it is likely that you made a configuration mistake. Correct the mistake and rerun the commands above to verify.
Configure NTP with Authorization Keys
For added security, you can configure NTP to use authorization keys.
Configure the NTP Server
Create a
.keys
file, such as/etc/ntp.keys
. Specify a key identifier (a number between 1 and 65535), an encryption method (M for MD5), and the password. The following provides an example:# # PLEASE DO NOT USE THE DEFAULT VALUES HERE. # #65535 M akey #1 M pass 1 M CumulusLinux!
In the
/etc/ntp.conf
file, add a pointer to the/etc/ntp.keys
file you created above and specify the key identifier. For example:keys /etc/ntp/ntp.keys trustedkey 1 controlkey 1 requestkey 1
Restart NTP with the
sudo systemctl restart ntp
command.
Configure the NTP Client
The NTP client is the Cumulus Linux switch.
Create the same
.keys
file you created on the NTP server (/etc/ntp.keys
). For example:cumulus@switch:~$ sudo nano /etc/ntp.keys # # DO NOT USE THE DEFAULT VALUES HERE. # #65535 M akey #1 M pass 1 M CumulusLinux!
Edit the
/etc/ntp.conf
file to specify the server you want to use, the key identifier, and a pointer to the/etc/ntp.keys
file you created in step 1. For example:cumulus@switch:~$ sudo nano /etc/ntp.conf ... # You do need to talk to an NTP server or two (or three). #pool ntp.your-provider.example # OR #server ntp.your-provider.example # pool.ntp.org maps to about 1000 low-stratum NTP servers. Your server will # pick a different set every time it starts up. Please consider joining the # pool: <http://www.pool.ntp.org/join.html> #server 0.cumulusnetworks.pool.ntp.org iburst #server 1.cumulusnetworks.pool.ntp.org iburst #server 2.cumulusnetworks.pool.ntp.org iburst #server 3.cumulusnetworks.pool.ntp.org iburst server 10.50.23.121 key 1 #keys keys /etc/ntp.keys trustedkey 1 controlkey 1 requestkey 1 ...
Restart NTP in the active VRF (default or management). For example:
cumulus@switch:~$ systemctl restart ntp@mgmt.service
Wait a few minutes, then run the
ntpq -c as
command to verify the configuration:cumulus@switch:~$ ntpq -c as ind assid status conf reach auth condition last_event cnt =========================================================== 1 40828 f014 yes yes ok reject reachable 1
After a successful authorization, you see the following command output:
cumulus@switch:~$ ntpq -c as ind assid status conf reach auth condition last_event cnt =========================================================== 1 40828 f61a yes yes ok sys.peer sys_peer 1
Considerations
NTP in Cumulus Linux uses the /usr/share/zoneinfo/leap-seconds.list
file, which expires periodically and results in generated log messages about the expiration. When the file expires, update it from https://www.ietf.org/timezones/data/leap-seconds.list or upgrade the tzdata
package to the newest version.