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  1. Configuring IP SLA
  2. Defining and Running an IP SLA Test Operation
  3. Using IP SLA
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From the author of Defining and Running an IP SLA Test Operation

Defining and Running an IP SLA Test Operation

You can use the following configuration steps to define and run an IP SLA test operation.

Step 1: Enable the IP SLA Responder on the Target Switch

Switch(config)# ip sla responder

By default, the IP SLA responder is disabled. If the IP SLA operation will involve jitter or time-critical measurements, then the responder should be enabled on the target switch.

Step 2: Define a New IP SLA Operation on the Source Switch

Switch(config)# ip sla operation-number

The operation-number is an arbitrary index that can range from 1 to a very large number. This number uniquely identifies the test.

Step 3: Select the Type of Test Operation to Perform

Switch(config-ip-sla)# test-type parameters...

The test-type keyword can be one of the following: dhcp, dns, ethernet, ftp, http, icmp-echo, mpls, path-echo, path-jitter, slm, tcp-connect, udp-echo, or udp-jitter.

The list of parameters following the test-type varies according to the test operation. As an example, consider the following icmp-echo operation syntax:

Switch(config-ip-sla)# icmp-echo destination-ip-addr [source-ip-addr]

The parameters are simple[md]a destination address to ping, and an optional source address to use. If a switch has several Layer 3 interfaces, you can specify which one of their IP address to use as the source of the test packets.

As another example, the udp-jitter command is useful for testing time-critical traffic paths through a switched network. The command syntax is a little more complex, as follows:

Switch(config-ip-sla)# udp-jitter destination-ip-addr dest-udp-port [source-ip
 source-ip-addr] [source-port source-udp-port] [num-packets number-of-packets]
 [interval packet-interval]

In addition to the source and destination IP addresses, you can define the UDP port numbers that will be used for the packet stream. By default, 10 packets spaced at 20 milliseconds will be sent. You can override that by specifying the num-packets and interval keywords.

As an alternative, you can configure the udp-jitter operation to test Voice Over IP (VoIP) call quality. To do this, the udp-jitter command must include the codec keyword and a codec definition. The IP SLA operation will then simulate a real-time stream of voice traffic using a specific codec. In this way, you can tailor the test to fit the type of calls that are actually being used in the network.

You can define the UDP jitter codec operation by using the following command syntax:

Switch(config-ip-sla)# udp-jitter destination-ip-addr dest-udp-port codec {g711alaw | g711ulaw | g729a} 

There are other keywords and parameters you can add to the command, but those are beyond the scope of this book. By default, 1,000 packets are sent, 20ms apart.

Step 4: Schedule the Test Operation

Switch(config)# ip sla schedule operation-number [life {forever | seconds}]
 [start-time {hh:mm[:ss] [month day | day month] | pending | now | after hh:mm:ss}]
 [ageout seconds] [recurring]

In a nutshell, the command tells the switch when to start the test, how long to let it run, and how long to keep the data that is collected.

Set the lifetime with the life keyword: forever means the operation will keep running forever, until you manually remove it. Otherwise, specify how many seconds it will run. By default, an IP SLA scheduled operation will run for 3600 seconds (one hour).

Set the start time with the start-time keyword. You can define the start time as a specific time, date, after a delay with the after keyword, or right now with the now keyword.

By default, the test statistics are collected and held in memory indefinitely. You can use the ageout keyword to specify how many seconds elapse before the data is aged out.

The recurring keyword can be used to schedule the test operation to run at the same time each day, as long as you have defined the starting time with hh:mm:ss, too.

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