Tips for configuring Cisco Network Time Protocol

For network security, the accuracy of NTP is crucial. Setting it correctly takes only a small amount of time to protect its security without any extra investment, but the security improvements will be very large. This article describes in detail how to set the network time.

Network Time Protocol (NTP) is a dedicated protocol based on User Datagram Protocol (UDP) that uses servers as clients and can be used to synchronize the time of network devices. Time Synchronization is a very important function for Virtual Private Networks and time-based access control lists. In addition, during network debugging, security testing, event Association, and other operations, it is also a very important factor.

NTP uses a concept called "layer". The so-called "layer" means that a device needs to "jump" several times to reach an authoritative time source. Here, layer 0 is based on one or a series of atomic clocks, which can provide a very accurate concept of time. Layer 1 means that it can directly obtain information from the 0-layer clock, so it just jumps once. In the case of Layer 3 and Layer 3, you can perform the following operations in sequence.

For the network, NTP is a very important factor, so you must ensure that it is correct and reliable. Therefore, the simplest and most feasible method is to establish a 1st-layer clock source in the network to provide accurate and reliable time sources. Generally, the most common method is to select a device in the network. Generally, it is a vro, Which is synchronized with a public time source at Layer 1st or layer 2nd as the main clock source of the local network.

Internal Devices, servers, and hosts can synchronize time with the network clock source. On the firewall, this layer allows you to complete NTP settings through UDP port 123.

The NTP authentication process can be ensured through routers and the NTP Access Control List, which can also improve network security.

Secure NIP

The NTP authentication method may be different from what you think. The key to the time for NTP authentication on a Cisco router is the source host (master clock), which uses the MD5 hash response. During NTP authentication, requests are sent from the client rather than from the router.

In this process, the integrity of the client source code sending the request is verified, rather than the customer's validity. This means that the router does not need to perform the usual authentication operation. However, if the client's authentication request is not approved by the router for configuration, the NTP synchronization operation will fail.

Therefore, to ensure the reliability and security of the network, you should set up multiple routers in it for automatic NTP synchronization. They should obtain time information from different 1st-layer time sources, A peer-to-peer authentication mechanism should also be established between these routers.

The access control list is a useful tool during NTP deployment. You can create a "peer group" Access Control List to authenticate and control network IP addresses to ensure the security of router connections. In addition, you can create a "service" or "service restriction" Access Control List to determine which network IP addresses or network clock on the router can be used for NTP query.

For Network Time Protocol Security, the accuracy of NTP is crucial. Setting it correctly takes only a small amount of time to protect its security without any extra investment, but the security improvements will be very large.