Configuring Health Monitoring Using Health Probes
This chapter describes how to configure a health probe on the Cisco 4700 Series Application Control Engine (ACE) appliance. This chapter contains the following sections:
•Configuring an HTTP Health Probe Using the Device Manager GUI
•Configuring an HTTP Health Probe Using the CLI
After reading this chapter, you should have a basic understanding of how the ACE appliance supports server health monitoring using health probes, and how to configure an HTTP health probe.
To detect failures and make reliable load-balancing decisions, you can configure the ACE appliance to track the health of servers and server farms by periodically sending out health probes (sometimes referred to as keepalives). By default, the ACE implicitly checks for server failures.
You can configure probes on the ACE to make active connections and explicitly send traffic to servers. The ACE evaluates the server's response to determine the health of that server.
When the ACE determines the health of a server, the result is one of the following:
•Passed—The server returned a valid response.
•Failed—The server failed to provide a valid response to the ACE within a specified number of retries.
When a server fails in response to the probe, the ACE can check for network problems that prevent a client from accessing that server. The ACE can place the server out of service.
A probe can be any of several types, including TCP, UDP, ICMP, Telnet, and HTTP. You can also configure scripted probes using the TCL scripting language.
You can configure a probe by following these steps:
Step 1 Create the probe and specify its name, type, and attributes.
Step 2 Associate the probe with one of the following:
•A real server.
•A real server that is associated with a server farm. You can associate a single probe or multiple probes to a real server within a server farm.
•A server farm. All real servers in the server farm receive the probe.
You can configure a probe by using either the ACE Device Manager GUI or the CLI. This chapter describes how to configure an HTTP probe. For information on how to configure other types of probes, see the Cisco 4700 Series Application Control Engine Appliance Server Load-Balancing Configuration Guide.
Configuring an HTTP Health Probe Using the Device Manager GUI
You can configure an HTTP health probe using the ACE Device Manager GUI by following these steps:
Step 1 Choose Load Balancing > Health Monitoring. The Health Monitoring pane appears (Figure 10-1).
Figure 10-1 Health Monitoring Pane
Step 2 Click Add to add a new health probe. The Health Monitoring window appears (Figure 10-2).
Figure 10-2 Health Monitoring Window
Step 3 Enter the following health probe attributes. Leave the remaining attributes blank or with their default values.
•Probe Interval (Seconds): 5
•Pass Detect Interval (Seconds): 10
Step 4 Click Deploy Now to deploy this configuration on the ACE appliance.
Step 5 Click the Expect Status tab at the bottom of the Health Monitoring window, then click Add to add a new health probe. The Expect Status configuration screen appears. (Figure 10-3).
Figure 10-3 Expect Status Configuration Screen
Step 6 Configure a single status code or a range of status code responses that the ACE expects from the probe destination. This parameter is required; without it, all HTTP or HTTPS probes will fail.
Enter a value of 200 for the Min. Expect Status Code and the Max. Expect Status Code.
Step 7 Click Deploy Now to deploy this configuration on the ACE appliance.
Step 8 Associate the health probe with a server farm by choosing Load Balancing > Server Farms. The Server Farms pane appears (Figure 10-4).
Figure 10-4 Server Farms Pane
Step 9 Choose the server farm SF_web and click Edit. The Server Farms window appears (Figure 10-5).
Figure 10-5 Server Farms Window
Step 10 For Probes, choose HTTP_probe1 from the Available list, and click the right-arrow button to move the probe to the Selected list.
Step 11 Click Deploy Now to associate the health probe HTTP_probe1 with the server farm SF_web.
Configuring an HTTP Health Probe Using the CLI
You can configure an HTTP health probe using the CLI by following these steps:
Step 1 Verify that you are operating in the desired context by checking the CLI prompt. If necessary, change to the correct context.
host1/Admin# changeto VC_web
Step 2 Enter configuration mode.
Step 3 Define an HTTP probe named HTPP_probe1 to access its configuration mode.
host1/VC_web(config)# probe http HTTP_probe1
Step 4 Configures a single status code or a range of status code responses that the ACE expects from the probe destination. This parameter is required; without it, all HTTP or HTTPS probes will fail.
host1/VC_web(config-probe-http)# expect status 200 200
Step 5 Configure port number 80 for the HTTP probe.
host1/VC_web(config-probe-http)# port 80
Step 6 Configure a time interval of 5 seconds between probes.
host1/VC_web(config-probe-http)# interval 5
Step 7 Configure a pass detect interval of 10 seconds, after which the ACE will send another probe to a failed server.
host1/VC_web(config-probe-http)# passdetect interval 10
Step 8 Exit probe configuration mode.
Step 9 Associate the probe HTTP_probe1 with the server farm SF_web, and exit configuration mode.
host1/VC_web(config)# serverfarm SF_web
host1/VC_web(config-sfarm-host)# probe HTTP_probe1
Step 10 Display the HTTP probe configuration.
host1/VC_web# show running-config probe
In this chapter, you have configured an HTTP health probe.