Cisco Network Time Protocol (NTP)

Lessons Discussion
27

Hello Kevin,

NTP authentication can be confusing. With your configuration, no authentication occurs because the client isn’t configured for authentication. I did a quick lab with your configuration.

The server will send “regular” NTP packets without an MD5 hash. Once you change the ntp server command on the client, it works.

Before:

https://www.cloudshark.org/captures/c40ea3a2748b

After:

Client(config)#ntp server 192.168.1.1 key 1

https://www.cloudshark.org/captures/e016b1c2e8a8

Once the client wants to use authentication, the server responds with the same MD5 hash. It doesn’t let you prevent clients from using your NTP server.

Hope this helps!

Rene

1 Like