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Cisco LocalDirector 400 Series

HTTP Probes on LocalDirector with 4.x Software Configuration Example

Document ID: 23641

Updated: Jan 31, 2006

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Introduction

This document provides a sample configuration to configure HTTP probes on the Cisco LocalDirector to use 4.x software.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Conventions

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

Background Information

In LocalDirector 4.x software, there is no support for Content Verification System/LocalDirector User Interface (CVS/LUI). There are no plans to support this product in any future revisions. For the 4.x software, the probe commands build into the command-line interface (CLI) the functionality that is present in the CVS/LUI interface.

You can use HTTP probes to determine if the back-end web servers are alive and respond on port 80. Many times, the TCP/IP stack is up and runs and responds to pings, but the web daemon has failed or is down for maintenance. The probe commands give the LocalDirector a way to determine this activity and put the server into the EFAILED. The send of new connections to the server occurs while the server is unable to respond. This action gives the LocalDirector a finer level of granularity to determine which web servers are available to serve content.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: To find additional information on the commands used in this document, use the Command Lookup Tool (registered customers only) .

Step-by-Step Instructions

This document uses this configuration:

  1. Define the type of probe.

    The command syntax is:

    probeconfig probe_type threshold
    
    

    For example:

    probeconfig http 1
    

    This command sets up an HTTP probe that runs every 10 seconds.

    Note: The 1 is the number of 10-second intervals to wait between probe attempts.

  2. Define the probe for the virtual.

    The command syntax is:

    probe {real | virtual} {real_id | virtual_id} probe_type number_of_intervals
    
    

    For example:

    probe virtual 10.86.16.224:80:0:tcp http 1
    
  3. Define the probe for the reals behind the virtual.

    The command syntax is:

    probe real 10.86.16.227:80:0:tcp http 2
    probe real 10.86.16.228:80:0:tcp http 1
    
    !--- There are two probes: one that runs every 20 seconds  
    !--- and one that runs every 10 seconds.
    
    
  4. Define the actual HTTP probe for the virtual.

    The command syntax is:

    probehttp {real | virtual} mach_id [file filename_path] [expected_return_code]
    [request {HEAD | GET}]
    

    For example:

    probehttp virtual 10.86.16.224:80:0:tcp file /default.asp
    
  5. Define the HTTP probe for the reals.

    This step is important because these settings override the settings for the virtual. Also, these settings are at the core of the reason that you want to set up probes. The settings can be different than that which you defined for the virtual.

    probehttp real 10.86.16.227:80:0:tcp file /default.asp
    probehttp real 10.86.16.228:80:0:tcp file /default.asp
    

The complete configuration is:

probe virtual 10.86.16.224:80:0:tcp http 1
probe real 10.86.16.227:80:0:tcp http 2
probe real 10.86.16.228:80:0:tcp http 1
probehttp virtual 10.86.16.224:80:0:tcp file /default.asp 
probehttp real 10.86.16.227:80:0:tcp file /default.asp
probehttp real 10.86.16.228:80:0:tcp file /default.asp
probeconfig http 1

Verify

This section provides information you can use to confirm that your configuration works properly.

Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.

Issue the show probeconfig command to verify this configuration.

localdirector(config)# show probeconfig
Type    Threshold
 dns    disabled
 http   1

localdirector(config)# show probe
Probes for Reals ----
        Machine                     Type     Interval

    10.86.16.227:80:0:tcp           http        2
    10.86.16.228:80:0:tcp           http        1

Probes for Virtuals ----
        Machine                     Type     Interval
    10.86.16.224:80:0:tcp           http        1

 localdirector(config)# show probehttp
                                                      Return
        Machine                       Port  Request   Code   Filename
    10.86.16.227:80:0:tcp (real)       80    HEAD     200      /default.asp 
    10.86.16.228:80:0:tcp (real)       80    HEAD     200      /default.asp 
    10.86.16.224:80:0:tcp (virtual)    80    HEAD     200      /default.asp 

localdirector(config)# show real
Real Machines:

                                                   No Answer TCP Reset DataIn
                  Machine  Connect   State  Thresh Reassigns Reassigns  Conns
    10.86.16.227:80:0:tcp       0      IS       8         0         0      0
    10.86.16.228:80:0:tcp       0      IS       8         0         0      0

When the probe fails, the server receives the mark EFAILED, as in this example:

localdirector(config)# show real
Real Machines:

                                                   No Answer TCP Reset DataIn
                  Machine  Connect   State  Thresh Reassigns Reassigns  Conns
    10.86.16.227:80:0:tcp       0 EFAILED       8         0         0      0
    10.86.16.228:80:0:tcp       0      IS       8         0         0      0      0

Note: The best version to use for this configuration is 4.2.3. Use of this version is important because there are some issues that arose with the use of probes; the 4.2.3 version cleaned up these issues.

Troubleshoot

This section provides information you can use to troubleshoot your configuration. Refer to these Cisco bug IDs for more information:

  • CSCdt64748 (registered customers only) —After a few probes, LocalDirector puts the real server in an EFAILED state. However, the real server is healthy and responds to HTTP requests.

  • CSCdu64435 (registered customers only) —After the placement of a virtual machine into the FAILED state, the send of HTTP probes to the real machines that are bound to the failed virtual machine is not successful.

  • CSCdv56353 (registered customers only) —Deletion or modification of an HTTP probe definition for an HTTP probe that actively probes causes the operation of the LocalDirector to stop.

Related Information

Updated: Jan 31, 2006
Document ID: 23641