Time synchronization is an important aspect for all computers on the network. By default, the clients computers get their time from a Domain Controller and the Domain Controller gets his time from the domain’s PDC Operation Master. Therefore the PDC must synchronize his time from an external source. I usually use the servers listed at the NTP Pool Project website. Before you begin, don’t forget to open the default UDP 123 port (in- and outbound) on your firewall.
First, locate your PDC Server. Open the command prompt and type: C:\>netdom /query fsmo
Log in to your PDC Server and open the command prompt.
Stop the W32Time service: C:\>net stop w32time
Configure the external time sources, type: C:\> w32tm /config /syncfromflags:manual /manualpeerlist:”0.pool.ntp.org, 1.pool.ntp.org, 2.pool.ntp.org”
Make your PDC a reliable time source for the clients. Type: C:\>w32tm /config /reliable:yes
Start the w32time service: C:\>net start w32time
The windows time service should begin synchronizing the time. You can check the external NTP servers in the time configuration by typing: C:\>w32tm /query /configuration
Check the Event Viewer for any errors.
Packet Sampling Basics
Configuring Extreme switches
The following commands configure an Extreme Networks switch (10.0.0.246), sampling packets at 1-in-512, polling counters every 30 seconds and sending the sFlow to an analyzer (10.0.0.50) over UDP using the default sFlow port (6343):
configure sflow agent 10.0.0.246
configure sflow collector 10.0.0.50 port 6343
configure sflow sample-rate 512
configure sflow poll-interval 30
enable sflow backoff-threshold
configure sflow backoff-threshold 100
enable sflow ports all
A previous posting discussed the selection of sampling rates. Additional information can be found on the Extreme Networks web site.
See Trying out sFlow for suggestions on getting started with sFlow monitoring and reporting.
Note: Extreme Networks switches support automatic backoff of sampling rates based on a settable samples-per-second threshold. This mechanism ensures that a poorly selected sampling rate will not generate excessive numbers of samples (see sFlow Version 5, section 4.2.2).
Posted by Peter at 9:30 PM
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