Information
At least one, and preferably three or more, external NTP Servers should be configured
Rationale:
Keeping time settings consistent across a network is vital if log data is to be meaningful and usable in understanding faults and security incidents. Consistent time settings are also fundamental to the operation of some network protocols and services such as IPSec, PKI and 802.1x which may be critical to many networks.
To ensure that the time on your JUNOS router is consistent with other devices in your network, at least one, and preferably three or more, NTP Servers external to the device should be configured.
Although NTP provides for a Peer to Peer type implementation, where individual time servers are not specified and methods such as broadcast and multicast are utilized to synchronize time between hosts, in almost all real world cases a Server / Client model should be used for network devices - even if multicast or broadcast methods are used for other types of hosts. Using specified time sources allows you to better secure, monitor and manage your NTP implementation; simplifying debugging and allowing tighter control of NTP traffic.
While a complete discussion of NTP Architecture is beyond the scope of this Benchmark, it is strongly recommended that careful attention be paid to resilience, accuracy and reliability of NTP time sources used within your network.
Having multiple NTP servers helps to ensure fault tolerance and also protects against mis-configured or compromised servers causing radical time changes, something an attacker may want to achieve to cover their tracks or conduct replay attacks.
Impact:
If time is not synchronised between devices, log messages cannot readily be correlated to allow administrators to understand events on the network. In addition, many services such as IPSEC, PKI or 802.1x which rely on Encryption may not function correctly if time and date settings are not properly maintained.
Solution
Configure at least one External NTP Server using the following commands under the [edit system] hierarchy;
[edit system]
user@host#set ntp server <Servers IP>
Default Value:
By default Juniper routers do not have NTP servers configured and use locally managed time.