NTP access-group options

[chinpohpang851]

I still don't quite understand the option Peer, serve and query-only. I have some understanding about Peer, so both devices will compare each other to see which one's better but what criteria are they comparing (Stratum numer) and how the better one sync the time to other device?

"Serve" will allowed sync n query request but not updating its own clock right?

"query-only" what kind of query control ntp does? 

[marce1000]

 1) serve - Allows time requests and NTP control queries, but does not allow the switch to synchronize itself to a device whose address passes the access list criteria.

 2) serve-only - Allows only time requests from a device whose address passes the access list criteria.

 3) query-only - Allows only NTP control queries from a device whose address passes the access list criteria.

 M.

[balaji.bandi]

herre is very good explanation Cisco design point of view

https://www.cisco.com/c/en/us/support/docs/availability/high-availability/19643-ntpm.html

[chinpohpang851]

any helpful article? I still can't find an article that explain the options.

[chinpohpang851]

let's assume R1(ntp server) and R2 (client) and Peer option is used under R1, does it mean R2's time can also overwrite R1's clock?