If you are a network administrator or network security administrator, managing large number of network infrastructure devices (Routers, Switches, Servers, Computers etc), it is very important to know that device time is a important factor in network security. Many authentication protocols will fail to work if you are different system time configured in different devices in your network. Following are the important network security related elements where Time is a crucial factor.
Kerberos authentication protocol: Kerberos authentication protocol (most widely used authentication protocol) will not work if there is a big time difference between the KDC (Key Distribution Center) and a client requesting tickets. The default Kerberos time skew allowed is 5 minutes. This is to prevent replay attacks.
Syslogs: When you track syslogs, it is crucial that all the Routers, Switches and Servers are configured with same time. If you have different time in different devices, it is difficult to correlate events happened in different devices. Therefore, it is important that the time on all the network infrastructure devices are synchronized properly.
Digital Certificates: Digital Certificates include a validity period. If your Cisco Router/Switch clock is not configured properly, Digital Certificates may not work properly.
NTP (Network Time Protocol) is a time synchronization protocol, which can be used to synchronize the system time of network infrastructure devices (Routers, Switches, Servers, Computers etc) from an external source. If you are new to NTP (Network Time Protocol), click the following link to learn more about NTP (Network Time Protocol) .