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time

Cisco cable-diagnostics with TDR

Some Cisco switches have a way to check the condition of copper cables. This can be done via de command test cable-diagnostics tdr. TDR stands for Time Domain Reflector. More information about Time Domain Reflector can be found at the Cisco Support Community.

The command can be very useful for basic layer 1 troubleshooting.

core01#test cable-diagnostics tdr int gig 5/0/21
TDR test started on interface Gi5/0/21
A TDR test can take a few seconds to run on an interface
Use ‘show cable-diagnostics tdr’ to read the TDR results.
core01#show cabl
core01#show cable-diagnostics tdr int gig 5/0/21
TDR test last run on: August 26 10:10:28

Interface Speed Local pair Pair length        Remote pair Pair status
——— —– ———- —————— ———– ——————–
Gi5/0/21  1000M Pair A     5    +/- 10 meters Pair A      Normal
Pair B     4    +/- 10 meters Pair B      Normal
Pair C     4    +/- 10 meters Pair C      Normal
Pair D     4    +/- 10 meters Pair D      Normal

The output above shows a successful measurement. The next example shows a failing cable-diagnostics test.

core01#test cable-diagnostics tdr interface gigabitEthernet 5/0/22
Link state may be affected during TDR test
TDR test started on interface Gi5/0/22
A TDR test can take a few seconds to run on an interface
Use ‘show cable-diagnostics tdr’ to read the TDR results.
core01#show cable-diagnostics tdr interface gig 5/0/22
TDR test last run on: August 26 10:04:43

Interface Speed Local pair Pair length        Remote pair Pair status
——— —– ———- —————— ———– ——————–
Gi5/0/22  100M  Pair A     N/A                Pair B      Normal
Pair B     N/A                Pair A      Fail
Pair C     N/A                Pair D      Normal
Pair D     N/A                Pair C      Normal

CactiEZ – configuration basics

Every time I install CactiEZ or Cacti on another platform, I am searching for the commands to basically install the most common parameters, like static IP addressing, NTP sync and time zones.

Several times I thought about writing a simple article with the necessary commands and final I had time to create it.

Networking

netconfig
service network restart

Time Sync

ntpdate –u ntp1.nl.net

Time Zone

yum install system-config-date
system-config-date

This will make my life so much easier.

Cacti Plugin Management and RealTime Plugin

I played a little with Cacti today and installed the Plugin Architecture 2.1. While reading some forums a lot of people are talking about the Plugin Management functionality. I looked and searched in my complete Cacti installation, checked all the configurations which can be made, but I couldn’t find anything about Plugin Management.

After some more searching on forums I found how to enable the Plugin Management. When you download the Plugin Architecture ZIP file, the ZIP contains a file called pa.sql. This file needs to be imported into the Cacti database with the following command:

mysql -u root -p cacti < pa.sql

After executing the command you can enable Plugin Management per user under User Management.

I haven’t played a lot with Cacti lately, but my colleague told me about a new plugin. This new plugin in called Realtime and I find it very useful. As you all know, Cacti only polls after a certain amount of minutes. Sometimes it is useful to get real-time bandwidth utilization statistics. In most cases I always use tools like STG or Interface Traffic Indicator (both can be found on the Tools page) to get real-time statistics. The Realtime plugin allows you to get real-time bandwidth utilization statistics through Cacti. You can download the Realtime plugin here, more information can be found at CactiUsers.org.

Telnet Time-Out is killing me….

Aaarrrgggghhh, I hate it when I would like to telnet into a device and enter the wrong IP address. This means, by default, waiting for 30 seconds before being able to correct the IP address and start a new telnet session, because there is no escape sequence.

SW01#telnet 10.100.12.250
Trying 10.100.12.250 …
% Connection timed out; remote host not responding

Luckily there is a command to lessen the time for timing out the connection:

SW01(config)# ip tcp synwait-time <seconds>       (Set time to wait on new TCP connections)

Hoera, tcp synwaiting saves the day….

Tools Page updated

I added a new tool to the Tools page, called Interface Traffic Indicator. The tool can be compared to STG, but needs to be installed on a workstation. The tool can be used to measure the throughput of a specific interface. To use the tool, you need at least the IP address of the device and a SNMP Read-Only string.

Tools like this can come in handy when measuring the used bandwidth of an interface in real-time. Appliance, like Cacti and Nagios, often poll ones in five minutes, which is very useful for establishing a baseline, but not for troubleshooting real-time.

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More information about the Interface Traffic Indicator can be found here.