There are three possible relationships that ntp can establish.
- client-server
- peer-peer
- sending broadcasts
With „ntp server“ only the client can get the time from the server.
With „ntp peer“ there is a peering relationship established and both can get the time from each other, regarding to the lower stratum.
As for example, i have router A, B and C. B is configured as a clients of A with „ntp server A“.
So A will provide the time for B. B will only get the time from A.
C is configured with „ntp peer B“. So C and B will share time information and can syncronize to each other, depending on which one has a better stratum.
All routers configured with the peer command can be „bound“ together inside a full mesh, where then every router is participating in the best time sync.