7.40 Implement Network Time Protocol

While reading about NTP for exam preparation, I got an idea to put short notes from Cisco Doc CD.
Doc CD path : Cisco IOS Network Management Configuration Guide, Release 12.4
http://www.cisco.com/en/US/docs/ios/netmgmt/configuration/guide/nm_basic_sys_manage_ps6350_TSD_Products_Configuration_Guide_Chapter.html
http://www.cisco.com/en/US/docs/ios/netmgmt/command/reference/nm_10.html

ntp access-group
To control access to the Network Time Protocol (NTP) services on the system
Router(config)# ntp access-group peer 99
Router(config)# ntp access-group serve-only 42

ntp authenticate
To enable Network Time Protocol (NTP) authentication, use the ntp authenticate command in global configuration mode.
Router(config)# ntp authenticate Router(config)# ntp authentication-key 42 md5 aNiceKey Router(config)# ntp trusted-key 42

ntp authentication-key
To define an authentication key for Network Time Protocol (NTP), use the ntp authentication-key command in global configuration mode. Only MD5 is supported

ntp broadcast
To configure the options for broadcasting Network Time Protocol (NTP) traffic, use the ntp broadcast command in interface configuration mode.
Router(config)# interface ethernet 0
Router(config-if)# ntp broadcast version 2

ntp broadcast client
To configure a device to receive Network Time Protocol (NTP) broadcast messages on a specified interface, use the ntp broadcast client command in interface configuration mode. Router(config)# interface ethernet 1
Router(config-if)# ntp broadcast client

ntp broadcastdelay
To set the estimated round-trip delay between the Cisco IOS software and a Network Time Protocol (NTP) broadcast server, use the ntp broadcastdelay command in global configuration mode.
Command Default - 3000 microseconds Use when the router is configured as a broadcast client and the round-trip delay on the network is other than 3000 microseconds

ntp clock-period
Information Only. Do not manually set a value for the NTP clock-period. The system automatically generates this command as Network Time Protocol (NTP) determines the clock error and compensates.

ntp disable
To prevent an interface from receiving Network Time Protocol (NTP) packets, use the ntp disable command in interface configuration mode.
Router(config)# interface ethernet 0
Router(config-if)# ntp disable

ntp logging
To enable Network Time Protocol (NTP) message logging, use the ntp logging command in global configuration mode.
Router(config)# ntp logging

ntp master
To configure the Cisco IOS software as a Network Time Protocol (NTP) master clock to which peers synchronize themselves when an external NTP source is not available, use the ntp master command in global configuration mode.
Router(config)# ntp master 10

ntp max-associations
To configure the maximum number of Network Time Protocol (NTP) peers and clients for a routing device, use the ntp max-associations command in global configuration mode. Specifies the number of NTP associations. The range is 0 to 4294967295. The default is 100.
Router(config)# ntp max-associations 200

ntp multicast
To configure a system to send Network Time Protocol (NTP) multicast packets on a specified interface, use the ntp multicast interface configuration command. Default - IPV4 - 224.0.1.1, IPV6- FF02:1 Default - ttl - 16, range 1-255 (limit the scope of an audience for multicast routing)
Router(config)# interface ethernet 0
Router(config-if)# ntp multicast version 2

ntp multicast client
To configure the system to receive Network Time Protocol (NTP) multicast packets on a specified interface, use the ntp multicast client interface configuration command.
Router(config)# interface ethernet 1
Router(config-if)# ntp multicast client
Default - 224.0.1.1

ntp peer
To configure the software clock to synchronize a peer or to be synchronized by a peer, use the ntp peer command in global configuration mode. The default maxpoll number is 10 seconds. The default minpoll number is 6 seconds.
When a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IPv4 or IPv6 address is taken from the outgoing interface.
To achieve faster NTP synchronization, enable the burst or iburst modes by using the burst or iburst keywords.
Router(config)# ntp peer 192.168.22.33 version 2 source ethernet 0
Router(config)# ntp peer 2001:0DB8:0:0:8:800:200C:417A version 4

ntp refclock
To configure an external clock source for use with Network Time Protocol (NTP) services, use the ntp refclock command in line configuration mode. Line configuration (for auxilary 0 only) Router(config)# ntp master
Router(config)# ntp update-calendar
Router(config)# line aux 0
Router(config-line)# ntp refclock trimble pps none

ntp server
To allow the software clock to be synchronized by a Network Time Protocol (NTP) time server, use the ntp server command in global configuration mode. Use this command if you want to allow the system to synchronize with the specified server. The server will not synchronize to this machine.
Router(config)# ntp server 172.16.22.44
Router(config)# ntp server 2001:0DB8:0:0:8:800:200C:417A version 4

ntp source
To use a particular source address in Network Time Protocol (NTP) packets, use the ntp source command in global configuration mode. Source address is determined by the outgoing interface.
This command is useful if the address on an interface cannot be used as the destination for reply packets.
Router(config)# ntp source ethernet 0
ntp trusted-key To authenticate the identity of a system to which Network Time Protocol (NTP) will synchronize, use the ntp trusted-key command in global configuration mode.
Router(config)# ntp authenticate
Router(config)# ntp authentication-key 42 md5 aNiceKey
Router(config)# ntp trusted-key 42

ntp update-calendar
To periodically update the hardware clock (calendar) from a Network Time Protocol (NTP) time source, use the ntp update-calendar command in global configuration mode.
Router(config)# ntp update-calendar

Other time setting command ref;
Manually Setting the Software Clock
Router# clock set hh:mm:ss date month year

Setting the Hardware Clock
Router> calendar set hh:mm:ss day month year

Setting the Software Clock from the Hardware Clock
Router# clock read-calendar

Setting the Hardware Clock from the Software Clock
Router# clock update-calendar

Monitoring Time and Calendar Services
Router# show calendar

Displays the current hardware clock time.
Router# show clock [detail]

Displays the current software clock time.
Router# show ntp associations [detail]

Displays the status of NTP associations.
Router# show ntp status

Displays the status of NTP.
Router# show sntp Displays information about SNTP (Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 routers only).