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Network Time Protocol

Network Time Protocol. Objectives to learn how to setup ntp Contents The NTP Server What is NTP? Download and Install The NTP Package The /etc/ntp.conf File How To Get NTP Started Determining If NTP Is Synchronized Properly. What is NTP?. Network Time Protocol

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Network Time Protocol

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  1. Network Time Protocol • Objectives • to learn how to setup ntp • Contents • The NTP Server • What is NTP? • Download and Install The NTP Package • The /etc/ntp.conf File • How To Get NTP Started • Determining If NTP Is Synchronized Properly

  2. What is NTP? • Network Time Protocol • Used to keep clock’s syncronized within your nodes • Important for logservers and logfiles • Transaction servers • Various applications • Time critic operations that needed to be syncronized • Stratum levels • Level 1 most accurate, many public exist • Level 2 next accurate, often companies timeservers • Lower levels • LW radio carriers as reference • Important atomic clock servers that supports NTP http://www.eecis.udel.edu/~mills/ntp/servers.html

  3. Download and Install The NTP Package • Check if NTP is there and then download it • Install NTP after it is downloaded • NTP is redhat standard, however it is not started. • First time chkconfig and service will open iptables firewall as well, ntp used port 123 UDP # ftp ftp.redhat.com ftp> cd /pub/redhat/linux/9/en/os/i386/RedHat/RPMS ftp> ls ntp* ftp> mget ntp* # rpm –ivh ntp-4.1.2-5.i386.rpm # chkconfig ntpd on # service ntpd start

  4. The /etc/ntp.conf File • First we specify the sample servers we're interested in: • Servers are used in order, average time can be calculated • Then we restrict the type of access you allow these servers • Declare the networks this NTP server should serve • This NTP server should serve itself unrestricted server  otherntp.server.org    # A stratum 1 server server  ntp.research.gov       # A srtatum 2 server restrict otherntp.server.org mask 255.255.255.255 nomodify notrap noquery restrict ntp.research.gov mask 255.255.255.255 nomodify notrap noquery restrict 192.168.0.0 mask 255.255.255.0 notrust nomodify notrap restrict 192.168.1.0 mask 255.255.255.0 notrust nomodify notrap restrict 127.0.0.1

  5. How To Get NTP Started • To get NTP configured to start at boot: • The demon is called ntpd • To start/stop/restart NTP after booting: • If you like with init scripts: • Logging in /var/log/messages • Logging in /var/log/ntpd.log # chkconfig ntpd on # service ntpd start # service ntpd stop # service ntpd restart # /etc/init.d/ntpd start # /etc/init.d/ntpd stop # /etc/init.d/ntpd restart

  6. Testing And Troubleshooting NTP • Verifying NTP is Running • you should get a response of plain old process ID numbers • Doing An Initial Synchronization against one server • First check current idea of time • Then syncronize against NTP server • Last check that time was adjusted • If time it was to big difference in time you might want to set the time as exact you can manually and do the sync again # pgrep ntpd # date Thu Sep 7 00:00:00 PDT 2004 # ntpdate –u ntp.research.gov Looking for host ntp.research.gov and service ntp host found : ntp.research.gov 7 Sep 08:03:38 ntpdate[2472]: step time server ntp.research.gov offset 28993.084943 sec # date Sep 7 08:03:38 PDT 2004

  7. Determining If NTP Is Synchronized Properly • With ntpq command see the servers you sync with • Jitter should be less than 100 • Try to use NTP server close to you with high strata level # ntpq -p      remote          refid       st t when poll reach  delay   offset   jitter==============================================================================-jj.cs.umb.edu   gandalf.sigmaso  3 u   95 1024  377  31.681  -18.549    1.572milo.mcs.anl.go  ntp0.mcs.anl.go  2 u  818 1024  125  41.993  -15.264    1.392-mailer1.psc.edu ntp1.usno.navy.  2 u  972 1024  377  38.206   19.589   28.028-dr-zaius.cs.wis ben.cs.wisc.edu  2 u  502 1024  357  55.098    3.979    0.333+taylor.cs.wisc. ben.cs.wisc.edu  2 u  454 1024  347  54.127    3.379    0.047-ntp0.cis.strath harris.cc.strat  3 u  507 1024  377 115.274   -5.025    1.642*clock.via.net   .GPS.            1 u  426 1024  377 107.424   -3.018    2.534ntp1.conectiv.c  0.0.0.0         16 u    - 1024    0   0.000    0.000  4000.00

  8. Your Linux NTP clients cannot Synchronize Properly • Your test show something like this • This could be caused by the following • Older versions of NTP must have IP addresses, not FDQN • A firewall blocking access to your Stratum 1 and 2 NTP servers, port 123 UDP must be opened. • Fedora Core 2 syncing to Feodora 2 client has a known bug # ntpq -p      remote           refid      st t when poll reach   delay   offset  jitter ==============================================================================  LOCAL(0)        LOCAL(0)        10 l    -   64    7    0.000    0.000   0.008  ntp-cup.externa 0.0.0.0         16 u    -   64    0    0.000    0.000 4000.00  snvl-smtp1.trim 0.0.0.0         16 u    -   64    0    0.000    0.000 4000.00  nist1.aol-ca.tr 0.0.0.0         16 u    -   64    0    0.000    0.000 4000.00

  9. Fedora / RedHat File Permissions • The /etc/ntpd catalog must have correct owner and group This catalog holds the drift file and network delay correction! chown ntp:ntp /etc/ntp

  10. Configuring Cisco Devices To Use An NTP Server • Cisco IOS • ntp server: Forms a server association with another system. • ntp update-calendar: Configures the system to update its hardware clock from the software clock at periodic intervals. ciscorouter> enable password: ********* ciscorouter# config t ciscorouter(config)# ntp update-calendarciscorouter(config)# ntp server 192.168.0.10ciscorouter(config)# ntp server 192.168.1.201ciscorouter(config)# exit ciscorouter# wr mem

  11. Configuring Cisco Devices To Use An NTP Server • CAT OS • ntp server: Forms a server association with another system. • set ntp client enable: Activate the NTP client ciscoswitch> enablepassword: *********ciscoswitch# set ntp client enableciscoswitch# ntp server 192.168.0.10ciscoswitch# ntp server 192.168.1.201 ciscoswitch# exit

  12. Summary • NTP server is adjust time and date on nodes • Configuration sit in /etc/ntpd.conf • Calibration files sit in /etc/ntpd/ • Strata levels tells system accuracy • Strata level 1 is most accurate • Stratalevel 2 is next accurate • Many applications rely on exact time • NTPD is the name of client and server demon • Show ntp status with ntpq –p • Update time manually: ntpdate –u ntp.research.gov • Most routers/Switches has NTP timesettings

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