An Overview of NTP

Question 1

NTP (Network Time Protocol)

Answer 1

• Switches, routers, firewalls, servers, workstations
  
  • Every device has its own clock
• Synchronizing the clocks becomes critical
  
  • Log files, authentication information, outage details
• Automatic updates
  
  • No flashing 12:00 lights
• Flexible
  
  • You control how clocks are updated

• Very accurate
• Accuracy is better than 1 millisecond on a local
network

Question 2

NTP stratum layers

Answer 2

• Some clocks are better than others
• Your distance from the original reference clock is a
stratum

• Stratum 0
  
  • Atomic clock, GPS clock
  • Very accurate
• Stratum 1
  
  • Synchronized to stratum 0 servers
  • Primary time servers
• Stratum 2
  
  • Sync’d to stratum 1 servers

Question 3

NTP clients and servers

Answer 3

• NTP server
  
  • Respond to time requests from NTP clients
  • Does not modify their own time
• NTP client
  
  • Requests time updates from NTP server
• NTP client/server
  
  • Requests time updates from an NTP server
  • Responds to time requests from other NTP clients

• Important to plan your NTP strategy
• Which devices are clients, servers, and
client/servers?

Question 4

Configuring NTP

Answer 4

• NTP client
• Specify the NTP server address (IP or hostname)
• Use multiple NTP servers (if available) for
redundancy

• NTP server
  
  • You need at least one clock source
  • Specify the stratum level of the clock
  • If there’s a choice, the lower stratum level wins