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. It outlines how to configure an HTTP probe.
This chapter contains the following sections:
•Information About Configuring Health Monitoring
•Prerequisites for Configuring Health Monitoring
•Configuring an HTTP Health Probe
•Configuration Example for an HTTP Health Probe
•Where to Go Next
Information About Configuring Health Monitoring
After reading this chapter, you should have a basic understanding of how the ACE supports server health monitoring using health probes (sometimes referred to as "keepalives"), and how to configure an HTTP health probe.
To detect failures and make reliable load-balancing decisions, you can configure the ACE to track the health of servers and server farms by periodically sending out health probes. 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 HTTP, HTTPS, ICMP, TCP, Telnet, and UDP. You can also configure scripted probes using the TCL scripting language.
For information on how to configure other types of probes, see the Server Load-Balancing Guide, Cisco ACE Application Control Engine.
Prerequisites for Configuring Health Monitoring
Before you can configure health monitoring, you must configure one or more servers or a server farm. For details, see Chapter 6, Configuring Server Load Balancing.
Configuring an HTTP Health Probe
To configure health monitoring, you can use either the ACE Device Manager user interface (GUI) or the CLI.
•Configuring an HTTP Health Probe Using the Device Manager GUI
•Configuring an HTTP Health Probe Using the CLI
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.
Step 2 Click Add (+) to add a new health probe. The Health Monitoring window appears.
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.
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.
Step 9 Choose the server farm SF_web and click Edit. The Server Farms window appears.
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
Configuration Example for an HTTP Health Probe
The following example shows how to configure an HTTP health probe. The commands that you have configured in this chapter appear in bold text.
switch/VC_web(config)# do show running config
access-list INBOUND line 8 extended permit ip any any
description content server web-one
description content server web-two
description content server web-three
description content server web-four
predictor hash header Accept
sticky http-cookie Cookie1 StickyGroup1
ssl-proxy service SSL_PSERVICE_SERVER
class-map match-all CM_SSL
2 match virtual-address 10.10.40.11 tcp eq https
class-map type management match-any REMOTE_ACCESS
description Remote access traffic match
3 match protocol telnet any
4 match protocol icmp any
class-map match-all VS_WEB
2 match virtual-address 10.10.40.10 tcp eq www
policy-map type management first-match REMOTE_MGMT_ALLOW_POLICY
policy-map type loadbalance first-match PM_LB
policy-map multi-match PM_MULTI_MATCH
loadbalance vip inservice
policy-map multi-match PM_SSL
ssl-proxy server SSL_PSERVICE_SERVER
service-policy input REMOTE_MGMT_ALLOW_POLICY
description Client connectivity on VLAN 400
ip address 10.10.40.1 255.255.255.0
access-group input INBOUND
service-policy input PM_MULTI_MATCH
service-policy input PM_SSL
description Server connectivity on VLAN 500
ip address 10.10.50.1 255.255.255.0
ip route 0.0.0.0 0.0.0.0 172.25.91.1
username USER1 password 5 $1$vAN9gQDI$MmbmjQgJPj45lxbtzXPpB1 role SLB-Admin domain
Where to Go Next
In this chapter, you have configured an HTTP health probe. In the next chapter, you will configure the the ACE for redundancy.