gf100,
Код:

cisco871#conf t
Enter configuration commands, one per line. End with CNTL/Z.
cisco871(config)#ntp ?
access-group Control NTP access
authenticate Authenticate time sources
authentication-key Authentication key for trusted time sources
broadcastdelay Estimated round-trip delay
clock-period Length of hardware clock tick
logging Enable NTP message logging
master Act as NTP master clock
max-associations Set maximum number of associations
peer Configure NTP peer
server Configure NTP server
source Configure interface for source address
trusted-key Key numbers for trusted time sources