Enabled the authenticated NTP service on the S7706, but the AR cannot synchronize the clock from the S7706.

Latest reply: Apr 20, 2018 11:50:09 534 1 0 0
 Issue Description

customer enabled the authenticated NTP service on the S7706, but the AR cannot synchronize the clock from the S7706.

Strangely, through capturing packets, the AR sends packets with authentication but the S7706 responds without authentication. Therefore, the AR does not trust the clock source and cannot be authenticated.

 

#core switch, NTP server

f4231075ae3d4cd3b5a465514a103a63


#AR router1 (V200R007C00SPCb00)

501b86ca402d495fa836b12d506824c1

transparent.gif Handling Process

Reproduce the issue and do capture to analysis.

We build the same environment of the existing network in the laboratory and can reproduce the issue. Through the capture, we find that the server checks the length of the Authentication Code while authenticating the client's synchronization packet. The length of hmac-sha256 algorithm is not right. The length of the Authentication Code should be 36, but the length of AR device is 20. The length of the string can also be seen from capturing the packet:


b8a7815c7bc24aee86a493f37b6227d7


Actually, the length of MD5 should be 20.

transparent.gif Root Cause

It is confirmed that the length of the SHA2 algorithm at the AR product side is 20, which is inconsistent with the platform and subsequent patches are modified to be consistent with other products.

transparent.gif Solution

Use MD5 authentication can sync the NTP.

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wissal
MVE Created Apr 20, 2018 11:50:09 Helpful(0) Helpful(0)

useful document, thanks
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  • convention:

Telecommunications%20engineer%2C%20currently%20senior%20project%20manager%20at%20an%20operator%2C%20partner%20of%20Huawei%2C%20in%20the%20radio%20access%20network%20department%2C%20for%2020%20years%20I%20managed%20several%20types%20of%20projects%2C%20for%20the%20different%20nodes%20of%20the%20network.

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