Cable Modem Troubleshooting Tips
When sending e-mails or posting news, the PC's clock will be used to timestamp the message. It is therefore helpful to others if your PC's date and time are kept correct. This can be done manually, and/or with automatic assistance
The best way of automatically synchronising computer clocks is to use the Network Time Protocol (NTP, sometimes known as SNTP, not to be confused with NNTP or SMTP) on port 123. The NTP system is capable of synchronising computer clocks with an accuracy of a few scores of microseconds. To use NTP you need to:
- identify an NTP server close to you (the closer the better);
- Windows 9x/ME/NT only: acquire an NTP client;
- configure NTP client software.
Typical places to try for an NTP server are (use the first of this list that works for you, on the principle of using the closest NTP server possible):
- Your UBR might support NTP: use the public Default Gateway IP address for the UBR rather than its private IP address. In the original NTL regions, and on Blueyonder, the UBR does support NTP, although some particular UBRs are giving problems. In the ex-C&W regions of NTL (where cable modem service is provided from a Pace digital TV STB), the UBR does support NTP for customers via the Default Gateway address. In general, the UBR does not support older time protocols such as DayTime (port 13) or Time (port 37).
- Your DHCP server: see Finding the DHCP server address. In the ex-C&W regions of NTL (where cable modem service is provided from a Pace digital TV STB), the DHCP server does not support NTP for customers.
- A time server provided by your ISP, if any:
- On NTL, use time.cableol.net
- On Blueyonder, use ntp.blueyonder.co.uk
For all Windows users, first ensure that the PC is in the correct timezone, and set the time manually:
- Open Control Panel.
- Double-click Date/Time.
- [WinNT/2000/XP] Click tab Time Zone.
- In the pull-down, select (GMT) Greenwich Mean Time: Dublin, Edinburgh, Lisbon, London.
- Check Automatically adjust clock for daylight saving changes.
- [WinNT/2000/XP] Click tab Date & Time.
- Adjust the date and time to be correct.
- Click OK.
Windows 9x/ME/NT: For automatic synchronisation, some popular time clients (e.g. WorldTime, TimeSync) do not support the NTP protocol. The following freeware applications support NTP synchronisation:
Set up AboutTime as follows:
- Click the tab Time Hosts.
- Click button Add.
- In the box Site name type a descriptive name of your choice.
- In the box Host name/address type the IP address of the NTP server that you discovered.
- In the dropdown Protocol select SNTP.
- Click Verify Entry, then click OK.
- Click the tab Control/Time Client.
- Click Set Time.
- Click Hide.
Windows 2000 has an NTP client built-in, a very smart one which not only synchronises your clock but also tweaks the rate of the clock so that it keeps better time anyway. If the Windows Time service is not already started, set it up as follows:
- In a Command Prompt window, type the command
net time /setsntp:xxx.xx.xxx.xxx
where xxx.xxx.xxx.xxx is the address of the NTP server that you discovered.
- Right-click on My Computer and select Manage.
- In the left-hand window, expand Services and Applications and select Services.
- In the right-hand window, scroll down and double-click Windows Time.
- In the drop-down Startup type select Automatic.
- Click button Start (unless it was already started, when the button is dimmed).
- Click OK.
- Close the window Computer Management.
This setup will automatically start the time synchroniser after every restart. If the Windows Time service had already been started, then just use the following commands:
net stop "Windows Time"
net time /setsntp:xxx.xxx.xxx.xxx
net start "Windows Time"
where xxx.xxx.xxx.xxx is the DNS name or IP number of the new NTP server. [Thanks to NiShFiSh for this Windows 2000 information].
Windows XP supports network time synchronisation. As installed, it synchronises automatically to a Microsoft time server in the USA. To select a closer time server:
- Open the Control Panel Date and Time.
- Click the tab Internet Time.
- Check Automatically synchronize with an Internet time server.
- In the box Server type the IP address or DNS name of the desired NTP time server.
- Click Update Now to check that it works. If it doesn't work, go back and set another server.
- Click OK.
This simple XP service synchronises with the server only once a week.
Apple Mac OS 8.5 to 9.2: has an NTP client incorporated into the Date & Time control panel. Set it up as follows:
- Open the control panel Date & Time.
- Check Set Daylight-Saving Time Automatically.
- If the timezone shown is not correct, click Set Time Zone...
- Scoll and select London, Cardiff, Edinburgh, or Dublin as appropriate.
- Click OK.
- Correct the date and time if necessary.
- For automatic synchronisation, check Use a Network Time Server.
- Click Server Options...
- From the drop-down Network Time Server, select Edit List...
- Click the button Add...
- In the box Descriptive name: type a name of your choice.
- In the box Server address: type the IP address of the NTP server that you discovered.
- Click Add.
- Ensure the new entry is selected, and click Done.
- Check and set a suitable refresh rate (e.g. 24 hours).
- Click the button Set Time Now.
- Click OK.
- Close the control panel.
Apple Mac OS X:
- Pull down the Apple menu, select System Preferences...
- Click Date & Time.
- Click tab Time Zone:
- Click on the world map in your part of the world;
- In the pull-down Closest City, select the name of the most suitable close city in your time zone.
- Click tab Date & Time:
- Use the controls to set the correct date and time.
- For automatic syncronisation, click tab Network Time:
- Check Use a network time server;
- In the box NTP Server, enter the address of your chosen NTP server, or select one of the pre-set ones in the drop-down;
- Click Set Time Now;
- Check you get the message Synchronization Succeeded, otherwise configure a different server.
Linux users should create or edit the file /etc/ntp.conf to contain the line:
where xxx.xxx.xxx.xxx is the NTP server address that you discovered. Starting the NTP client daemon varies according to system: for RedHat 7.0 give the command:
chkconfig --level 345 ntpd on
RedHat 6.2 uses xntpd instead of ntpd. [Thanks to Jon Peatfield for this Linux information].
Other platforms: see http://www.eecis.udel.edu/~ntp/software.html.
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