Cisco Explorer 4700 Installation Guide download pdf (Page 224)

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Device Manager Guide, Cisco ACE 4700 Series Application Control Engine Appliance

OL-26645-02

Chapter 6 Configuring Real Servers and Server Farms

Configuring Server Farms

Inband-Health Check This field appears only for host server farms.

By default, the ACE monitors the health of all real servers in a configuration through the use of

ARPs and health probes. However, there is latency period between when the real server goes down

and when the ACE becomes aware of the state. The inband health monitoring feature allows the

ACE to monitor the health of the real servers in the server farm through the following connection

failures:

• For TCP, resets (RSTs) from the server or SYN timeouts.

• For UDP, ICMP Host, Network, Port, Protocol, and Source Route unreachable messages.

When you configure the failure-count threshold and the number of these failures exceeds the

threshold within the reset-time interval, the ACE immediately marks the server as failed, takes it

out of service, and removes it from load balancing. The server is not considered for load balancing

until the optional resume-service interval expires.

Choose one of the following:

• Count—Tracks the total number of TCP or UDP failures, and increments the counters as

displayed by the show serverfarm name inband CLI command.

• Log—Logs a syslog error message when the number of events reaches the configured

connection failure threshold.

• Remove—Logs a syslog error message when the number of events reaches the threshold and

removes the server from service.

Note You can configure this feature and health probes to monitor a server. When you do, both are

required to keep a real server in service within a server farm. If either feature detects a

server is out of service, the ACE does not select the server for load balancing.

Connection Failure

Threshold Count

This field appears only when the Inband-Health Check is set to Log or Remove.

Enter the maximum number of connection failures that a real server can exhibit in the reset-time

interval before ACE marks the real server as failed. Valid entries are integers from 1 to 4294967295.

Reset Timeout

(Milliseconds)

This field appears only when the Inband-Health Check is set to Log or Remove.

Enter the number of milliseconds for the reset-time interval. Valid entries are integers from 100 to

300000. The default interval is 100.

This interval starts when the ACE detects a connection failure. If the connection failure threshold

is reached during this interval, the ACE generates a syslog message.When Inband-Health Check is

set to Remove, the ACE also removes the real server from service.

Changing the setting of this option affects the behavior of the real server, as follows:

• When the real server is in the OPERATIONAL state, even if several connection failures have

occurred, the new reset-time interval takes effect the next time that a connection error occurs.

• When the real server in the INBAND-HM-FAILED state, the new reset-time interval takes

effect the next time that a connection error occurs after the server transitions to the

OPERATIONAL state.

Table 6-5 Server Farm Attributes (continued)

Field Description

1 ... 223 224 225 ... 648

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