The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
Simple Network Time Protocol (SNTP) is a simplified version of Network Time Protocol(NTP). This module describes how to configure Simple Network Time Protocol on Cisco devices.
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Simple Network Time Protocol (SNTP) is a simplified, client-only version of NTP. SNTP can receive only the time from NTP servers; it cannot be used to provide time services to other systems.
SNTP typically provides time within 100 milliseconds of the accurate time, but it does not provide the complex filtering and statistical mechanisms of NTP. In addition, SNTP does not authenticate traffic, although you can configure extended access lists to provide some protection. An SNTP client is more vulnerable to servers that have unexpected behavior than an NTP client, and should be used only in situations where strong authentication is not required.
You can configure SNTP to request and accept packets from configured servers or to accept NTP broadcast packets from any source. When multiple sources are sending NTP packets, the server with the best stratum is selected. (See the Network Time Protocol section on page 3 for a description of strata.) If multiple servers are at the same stratum, a configured server is preferred over a broadcast server. If multiple servers pass both tests, the first one to send a time packet is selected. SNTP will choose a new server only if it stops receiving packets from the currently selected server, or if a better server (according to the criteria described) is discovered.
Simple Network Time Protocol (SNTP) is a simplified version of Network Time Protocol (SNTP). This module describes how to configure SNTP on Cisco devices.
To verify information about the Simple Network Time Protocol, perform the following command.
To troubleshoot simple network time protocol, perform the following command.
Command or Action | Purpose | |
---|---|---|
|
Example: Device> debug sntp packets |
Displays the NTP packet sent and received along with the SNTP packet fields. |
|
Example: Device> debug sntp select |
Displays the SNTP server selection for IPv4 and IPv6 servers. |
clock timezone PST -8 clock summer-time PDT recurring sntp update-calendar sntp server 192.168.13.57 sntp server 192.168.11.58 interface Ethernet 0/0 sntp broadcast
Related Topic |
Document Title |
---|---|
Cisco IOS commands |
|
Basic System Management commands |
|
NTP4 in IPv6 |
Cisco IOS Basic System Management Guide |
IP extended access lists |
Cisco IOS IP Addressing Configuration Guide |
IPX extended access lists |
Novell IPX Configuration Guide |
NTP package vulnerability |
Network Time Protocol Package Remote Message Loop Denial of Service Vulnerability |
Cisco IOS and NX-OS software releases |
'White Paper: Cisco IOS and NX-OS Software Reference Guide |
Standard/RFCs |
Title |
---|---|
RFC 1305 |
Network Time Protocol (Version 3) Specification, Implementation and Analysis |
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 1 | Feature Information for Simple Network Time Protocol |
Feature Name |
Releases |
Feature Information |
---|---|---|
Simple Network Time Protocol |
Cisco IOS 15.3(2)T Cisco IOS 15.3(2)S Cisco IOS XE 3.9.0 S |
Simple Network Time Protocol (SNTP) is a simplified, client-only version of Network Time Protocol(SNTP) The following commands were introduced or modified: sntp server,sntp authenticate, sntp authentication-key, sntp multicast,sntp trusted-key. |
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.