Table Of Contents
Configuring Real Servers and Server Farms
Real Server Configuration Quick Start
Configuring a Real Server Description
Configuring a Real Server IP Address
Configuring Real Server Health Monitoring
Configuring Real Server Connection Limits
Configuring a Real Server Relocation String
Configuring a Real Server Weight
Placing a Real Server in Service
Gracefully Shutting Down a Server
Server Farm Configuration Quick Start
Configuring a Description of a Server Farm
Configuring the ACE Action on Server Failure
Associating Multiple Health Probes with a Server Farm
Configuring the Server Farm Predictor Method
Configuring Server Farm HTTP Return Code Checking
Associating a Real Server with a Server Farm
Configuring the Weight of a Real Server in a Server Farm
Configuring a Backup Server for a Real Server
Configuring Health Monitoring for a Server Farm
Configuring Connection Limits for a Real Server in a Server Farm
Placing a Real Server in Service
Gracefully Shutting Down a Server with Sticky Connections
Configuring a Backup Server Farm
Displaying Real Server Configurations and Statistics
Displaying Real Server Configurations
Displaying Real Server Statistics
Displaying Real Server Connections
Clearing Real Server Statistics and Connections
Clearing Real Server Statistics
Clearing Real Server Connections
Displaying Server Farm Configurations and Statistics
Displaying Server Farm Configurations
Displaying Server Farm Statistics
Displaying Server Farm Connections
Clearing Server Farm Statistics
Configuring Real Servers and Server Farms
This chapter describes the functions of real servers and server farms in load balancing and how to configure them on the Cisco Application Control Engine (ACE) module. It contains the following major sections:
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Displaying Real Server Configurations and Statistics
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Configuring Real Servers
This section describes real servers and how to configure them. It contains the following topics:
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Real Server Overview
Real servers are dedicated physical servers that you typically configure in groups called server farms. These servers provide services to clients, such as HTTP or XML content, streaming media (video or audio), TFTP or FTP uploads and downloads, and so on. You identify real servers with names and characterize them with IP addresses, connection limits, and weight values.
The ACE uses traffic classification maps (class maps) within policy maps to filter out interesting traffic and to apply specific actions to that traffic based on the SLB configuration. You use class maps to configure a virtual server address and definition. The load-balancing predictor algorithms (for example, round-robin, least connections, and so on) determine the servers to which the ACE sends connection requests. For information about configuring traffic policies for SLB, see Chapter 3, Configuring Real Servers and Server Farms.
Managing Real Servers
If a primary real server fails, the ACE takes that server out of service and no longer includes it in load-balancing decisions. If you configured a backup server for the real server that failed, the ACE redirects the primary real server connections to the backup server. For information about configuring a backup server, see the "Configuring a Backup Server for a Real Server" section.
The ACE can take a real server out of service for the following reasons:
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For servers with sticky connections, the ACE removes those sticky entries from the sticky database when it takes the server out of service. For more information about stickiness, see Chapter 5, Configuring Stickiness.
You can instruct the ACE to purge Layer 3 and Layer 4 connections if a real server fails by using the failaction purge command. The default behavior of the ACE is to do nothing with existing connections if a real server fails. For details about the failaction command, see the "Configuring the ACE Action on Server Failure" section. For Layer 7 connections, you can instruct the ACE to rebalance each HTTP request by entering the persistence-rebalance command. For details about the persistence-rebalance command, see the "Enabling HTTP Persistence Rebalance" section in Chapter 3, Configuring Traffic Policies for Server Load Balancing.
You can also manually take a primary real server out of service gracefully using either the no inservice command or the inservice standby command. Both commands provide graceful shutdown of a server. Use the no inservice command when you do not have stickiness configured and you need to take a server out of service for maintenance or a software upgrade. The no inservice command instructs the ACE to do the following:
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With sticky configured, use the inservice standby command to gracefully take a primary real server out of service. The inservice standby command instructs the ACE to do the following do the following:
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Real Server Configuration Quick Start
Table 2-1 provides a quick overview of the steps required to configure real servers. Each step includes the CLI command or a reference to the procedure required to complete the task. For a complete description of each feature and all the options associated with the CLI commands, see the sections following Table 2-1.
Creating a Real Server
You can configure a real server and enter real server configuration mode by using the rserver command in configuration mode. You can create a maximum of 16,384 real servers. The syntax of this command is as follows:
rserver [host | redirect] name
The keywords, arguments, and options for this command are as follows:
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For example, to create a real server of type host, enter:
host1/Admin(config)# rserver server1host1/Admin(config-rserver-host)#To remove the real server of type host from the configuration, enter:
host1/Admin(config)# no rserver server1To create a real server of type redirect, enter:
host1/Admin(config)# rserver redirect server2host1/Admin(config-rserver-redirect)#To remove the real server of type redirect from the configuration, enter:
host1/Admin(config)# no rserver redirect server2The sections that follow apply to both real server types unless otherwise indicated.
Configuring a Real Server Description
You can configure a description for a real server by using the description command in either real server host or real server redirect configuration mode. The syntax of this command is as follows:
description string
For the string argument, enter an unquoted alphanumeric text string with no spaces and a maximum of 240 characters.
For example, enter:
host1/Admin(config-rserver-host)# description accounting serverTo remove the real-server description from the configuration, enter:
host1/Admin(config-rserver-host)# no descriptionConfiguring a Real Server IP Address
Configure an IP address so that the ACE can access a real server of type host. See the "Configuring Real Servers" section.
You can configure an IP address by using the ip address command in either real server host or real server redirect configuration mode. The syntax of this command is as follows:
ip address ip_address
For the ip_address argument, enter a unique IPv4 address in dotted-decimal notation (for example, 192.168.12.15). The IP address must not be the address of an existing virtual IP address (VIP).
For example, to specify an address enter:
host1/Admin(config-rserver-host)# ip address 192.168.12.15To remove the real server IP address from the configuration, enter:
host1/Admin(config-rserver-host)# no ip addressConfiguring Real Server Health Monitoring
To check the health and availability of a real server, the ACE periodically sends a probe to the real server. Depending on the server response, the ACE determines whether to include the server in its load-balancing decision. For more information about probes, see Chapter 4, Configuring Health Monitoring.
You can assign one or more existing probes to a real server by using the probe command in real server host configuration mode. This command applies only to real servers of type host. The syntax of this command is as follows:
probe name
For the name argument, enter the name of an existing probe. Enter an unquoted text string with no spaces and a maximum of 64 alphanumeric characters.
For example, enter:
host1/Admin(config-rserver-host)# probe probe1To remove a real server probe from the configuration, enter:
host1/Admin(config-rserver-host)# no probe probe1Configuring Real Server Connection Limits
To prevent a real server from being overburdened, you can limit the maximum number of active connections to the server. You can set the maximum and minimum connection thresholds by using the conn-limit command in either real server host or real server redirect configuration mode. The syntax of this command is as follows:
conn-limit max maxconns min minconns
The keywords and arguments are as follows:
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Because the ACE has two network processors (NPs), the maxconns value for a real server is divided between the two NPs. If you configure an odd value for maxconns, one of the NPs will have a maxconns value that is one greater than the value on the other NP. With very small values for maxconns, it is possible for a connection to be denied, even though one of the NPs has the capacity to handle the connection.
Consider the scenario where you configure a value of 3 for the maxconns argument for a real server. One NP will have a value of 2 and the other NP will have a value of 1. If both NPs have reached their connection limits for that server, the next connection request for that server will be denied and the Out-of-rotation Count field of the show serverfarm detail command will increment by 1. Now, suppose a connection is closed on the NP with the maxconns value of 2. If the next connection request to the ACE goes to the NP with the maxconns value of 1 and it has already reached its limit, the ACE denies the connection, even though the other NP has the capacity to service the connection.
If you change the minconns value while there are live connections to a real server, the server could enter the MAXCONNS state without actually achieving the maxconns value in terms of the number of connections to it. Consider the following scenario where you configure a maxconns value of 10 and a minconns value of 5. Again, the ACE divides the values as equally as possible between the two NPs. In this case, both NPs would have a maxconns value of 5, while NP1 would have a minconns value of 3 and NP2 would have a minconns value of 2.
Suppose that the real server now has 10 live connections to it. Both NPs and the server have reached the MAXCONNS state. If four connections to the real server are closed leaving six live connections, both NPs (and, hence, the real server) would still be in the MAXCONNS state with three connections each. Remember, for an NP to come out of the MAXCONNS state, the number of connections to it must be less than the minconns value.
If you change the server's minconns value to 7, NP1 would enter the OPERATIONAL state because the number of connections (three) is one less than the minconns value of 4. NP2 would still be in the MAXCONNS state (minconns value = number of connections = 3). NP1 could process two more connections for a total of only eight connections to the real server, which is two less than the server's maxconns value of 10.
You can also specify minimum and maximum connections for a real server in a server farm configuration. The total of the minimum and maximum connections that you configure for a server in a server farm cannot exceed the minimum and maximum connections you set globally in real server configuration mode. For details about configuring real server maximum connections in a server farm configuration, see the "Configuring Connection Limits for a Real Server in a Server Farm" section.
For example, enter:
host1/Admin(config-rserver-host)# conn-limit max 5000 min 4000To reset the real-server maximum connection limit and minimum connection limit to the default values of 4294967295, enter:
host1/Admin(config-rserver-host)# no conn-limitConfiguring a Real Server Relocation String
You can configure a real server to redirect client requests to a location specified by a relocation string or a port number. You can configure a relocation string for a real server that you configured as a redirection server (type redirect) by using the webhost-redirection command in real server redirect configuration mode. The syntax of this command is as follows:
webhost-redirection relocation_string [301 | 302]
The keywords and arguments are as follows:
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For example, enter:
host1/Admin(config-rserver-redir)# webhost-redirection http://%h/redirectbusy.cgi?path=%p 302Assume the following client GET request:
GET /helloworld.html HTTP/1.1Host: www.cisco.comThe redirect response would appear as follows:
HTTP/1.1 302 FoundLocation: http://www.cisco.com/redirectbusy.cgi?path=/helloworld.htmlTo remove the relocation string from the configuration, enter:
host1/Admin(config-rserver-redir)# no webhost-redirection http://%h/redirectbusy.cgi?path=%p 302Configuring a Real Server Weight
You can configure the connection capacity of a real server of type host in relation to the other servers in a server farm by using the weight command in real server host configuration mode. The ACE uses the weight value that you specify for a server in the weighted round-robin and least connections load-balancing predictors. Servers with a higher configured weight value have a higher priority with respect to connections than servers with a lower weight. For example, a server with a weight of 5 would receive five connections for every one connection for a server with a weight of 1.
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To specify different weight values for a real server of type host in a server farm, you can assign multiple IP addresses to the server. You can also use the same IP address of a real server with different port numbers.
The syntax of this command is as follows:
weight number
The number argument is the weight value assigned to a real server in a server farm. Enter an integer from 1 to 100. The default is 8.
For example, enter:
host1/Admin(config-rserver-host)# weight 50To reset the configured weight of a real server to the default value of 8, enter:
host1/Admin(config-rserver-host)# no weightPlacing a Real Server in Service
Before you can start sending connections to a real server, you must place the server in service. You can place a real server in service by using the inservice command in either real server host or real server redirect configuration mode. The syntax of this command is as follows:
inservice
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For example, to place a real server in service, enter:
host1/Admin(config-rserver-host)# inserviceGracefully Shutting Down a Server
You can shut down a real server gracefully by using the no inservice command in either real server host or real server redirect configuration mode. This command causes the ACE to tear down all non-TCP connections to the server. For TCP connections, existing flows are allowed to complete before the ACE takes the real server out of service. No new connections are allowed.
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The syntax of this command is as follows:
no inservice
For example, to gracefully shut down a real server (for example, for maintenance or software upgrades), enter:
host1/Admin(config-rserver-host)# no inserviceConfiguring a Server Farm
This section describes server farms and how to configure them. It contains the following topics:
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Server Farm Overview
Server farms are groups of networked real servers that contain the same content and that typically reside in the same physical location in a data center. Web sites often comprise groups of servers configured in a server farm. Load-balancing software distributes client requests for content or services among the real servers based on the configured policy and traffic classification, server availability and load, and other factors. If one server goes down, another server can take its place and continue to provide the same content to the clients who requested it.
Server Farm Configuration Quick Start
Table 2-2 provides a quick overview of the steps required to configure server farms. Each step includes the CLI command or a reference to the procedure required to complete the task. For a complete description of each feature and all the options associated with the CLI commands, see the sections following Table 2-2.
Creating a Server Farm
You can create a new server farm or modify an existing server farm and enter the server-farm configuration mode by using the serverfarm command in configuration mode. You can configure a maximum of 16,384 server farms on each ACE.
The syntax of this command is as follows:
serverfarm [host | redirect] name
The keywords, arguments, and options are as follows:
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For example, to create a server farm of type host called SFARM1, enter:
host1/Admin(config)# serverfarm SFARM1host1/Admin(config-sfarm-host)#For example, to create a server farm of type redirect called SFARM2, enter:
host1/Admin(config)# serverfarm redirect SFARM2host1/Admin(config-sfarm-redirect)#After you create a server farm, you can configure the other server farm attributes and add real servers to it as described in the following sections:
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Configuring a Description of a Server Farm
You can provide a text description of a server farm by using the description command in either server farm host or server farm redirect configuration mode. The syntax of this command is as follows:
description text
For the text argument, enter a server farm description with a maximum of 240 alphanumeric characters.
For example, to enter a description of a server farm, enter:
host1/Admin(config-sfarm-host)# description CURRENT EVENTS ARCHIVETo remove the description of a server farm, enter:
host1/Admin(config-sfarm-host)# no descriptionConfiguring the ACE Action on Server Failure
You can set the action that the ACE takes with respect to connections if any real server fails in a server farm. You can configure the failure action by using the failaction command in either server farm host or server farm redirect configuration mode. The syntax of this command is as follows:
failaction purge
The purge keyword specifies that the ACE remove the connections to a real server if that real server in the server farm fails after you enter the command. The ACE sends a reset (RST) to both the client and the server that failed.
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For example, to remove connections from a failed server in the server farm, enter:
host1/Admin(config-sfarm-host)# failaction purgeTo reset the behavior of the ACE to the default of taking no action if a real server fails, enter:
host1/Admin(config-sfarm-host)# no failactionAssociating Multiple Health Probes with a Server Farm
You can associate multiple health probes of the same or different protocols with each server farm. Each server farm supports the following probe types:
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You can associate a probe with a server farm by using the probe command in server farm host configuration mode only. The syntax of this command is as follows:
probe name
For the name argument, enter the name of an existing probe as a text string with no spaces and a maximum of 64 alphanumeric characters. For information about configuring probes, see Chapter 4, Configuring Health Monitoring.
For example, enter:
host1/Admin(config-sfarm-host)# probe PROBE1To remove the probe from the server farm configuration, enter:
host1/Admin(config-sfarm-host)# no probe PROBE1Configuring the Server Farm Predictor Method
The load-balancing (predictor) method that you configure determines how the ACE selects a real server in a server farm to service a client request. You can configure the load-balancing method by using the predictor command in either server farm host or server farm redirect configuration mode. The syntax of this command is as follows:
predictor {roundrobin | leastconns [slowstart time] | hash {address [destination | source] [netmask] | cookie name1 | header name2 | url [begin-pattern text] [end-pattern text]}}
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The keywords and arguments are as follows:
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The optional slowstart time keyword and argument specify that the connections to the real server be in a slow-start mode. The ACE calculates a slow-start time stamp from the current time plus the time value that you specify. The ACE uses the timestamp as a fail-safe mechanism in case a real server stays in slow-start mode for a prolonged period of time (for example, with long-lived flows). Enter an integer from 1 to 65535 seconds. By default, slowstart is disabled.
Use the slow-start mechanism to avoid sending a high rate of new connections to servers that you have recently put into service. When a new real server enters slow-start mode, the ACE calculates and assigns an artificially high metric weight value to the new server and sends a small number of connections to the new server initially. The remaining connections go to the existing servers based on their weight and current connections.
The real server (including the new server) with the lowest calculation (weight × current connections) receives the next connection request for the server farm. Each time that the ACE assigns a new connection to the new real server, the ACE checks the validity of the timestamp. If the timestamp has expired, the ACE takes the server out of slow-start mode. As the new server connections are finished (closed), the ACE decrements both the new server connection count and the metric weight value by the number of closed connections.
A real server exits slow-start mode when one of the following events occurs:
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The ACE places real servers in slow-start mode only if they have no existing connections to them. For example, if you have two real servers (RSERVER1 and RSERVER2) in a server farm that have the same number of active connections to them, slow start is configured for 180 seconds, and you add a new real server (RSERVER3) to the server farm, the ACE places the new real server in slow-start mode and sends a small number of new connections to it. The ACE equally divides the remainder of the new connections between RSERVER1 and RSERVER2. At this point, if RSERVER1 goes into any failed state (for example, PROBE-FAILED or ARP-FAILED) and then later it is placed back in service within 180 seconds of RSERVER3's addition to the server farm, the ACE does not put RSERVER1 in slow-start mode because of the connections to RSERVER1 that existed before the out-of-service event.
Instead, the ACE sends most or all of the new connections to RSERVER1 in an effort to make the connection count the same as RSERVER2 and ignores RSERVER3, which is still in slow-start mode. When the connection count for RSERVER1 and RSERVER2 are similar, then the ACE resumes sending a small number of connections to RSERVER3 for the duration of the slow-start timer.
If RSERVER1 returns to the OPERATIONAL state more than 180 seconds after you added RSERVER3 to the server farm, then RSERVER3 will be out of slow-start mode. In this case, the ACE sends most or all of the new connections to RSERVER1 in an effort to make the connection count the same as RSERVER2 or RSERVER3, whichever has the least number of connections.
To ensure that a failed server with existing connections enters slow-start mode when it is placed back in service, configure failaction purge for the real server in a server farm. This command removes all existing connections to the real server if it fails. For details about the failaction purge command, see the "Configuring the ACE Action on Server Failure" section.
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For example, to select the server with the lowest number of connections in the server farm, enter:
host1/Admin(config-sfarm-host)# predictor leastconnsTo reset the predictor algorithm to the default of roundrobin, enter:
host1/Admin(config-sfarm-host)# no predictorConfiguring Server Farm HTTP Return Code Checking
You can configure HTTP return-code checking (retcode map) for a server farm by using the retcode command in server farm host configuration mode only. You can specify a single return code number or a range of return code numbers. For example, you can instruct the ACE to check for and count the number of occurrences of such return codes as HTTP/1.1 200 OK, HTTP/1.1 100 Continue, or HTTP/1.1 404 Not Found.
The syntax of this command is as follows:
retcode number1 number2 check count
The keywords, arguments, and options are as follows:
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You can configure multiple retcode maps on each server farm. You can view hit counts for retcode checking by using the show serverfarm command. For details, see the "Displaying Server Farm Statistics" section.
For example, to check for and count the number of return code hits for all return codes from 200 to 500 inclusive, enter:
host1/Admin(config-sfarm-host)# retcode 200 500 check countTo remove the HTTP return-code map from the configuration, enter:
host1/Admin(config-sfarm-host)# no retcode 200 500 check countAssociating a Real Server with a Server Farm
You can associate one or more real servers with a server farm and enter real-server server-farm configuration mode by using the rserver command in either server farm host or server farm redirect configuration mode. The real server must already exist. For information about configuring a real server, see the "Configuring Real Servers" section. You can configure a maximum of 16,384 real servers in a server farm. The syntax of this command is as follows:
rserver name [port]
The arguments are as follows:
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If you choose not to assign a port number for the real server association with the server farm, the default behavior by the ACE is to automatically assign the same destination port that was used by the inbound connection to the outbound server connection. For example, if the incoming connection to the ACE is a secure client HTTPS connection, the connection is typically made on port 443. If you do not assign a port number to the real server, the ACE will automatically use port 443 to connect to the server, which results in the ACE making a clear-text HTTP connection over port 443. In this case, you would typically define an outbound destination port of 80, 81, or 8080 for the back-end server connection.
For example, to identify real server SERVER1 and specify port 80 for the outgoing connection, enter:
host1/Admin(config-sfarm-host)# rserver SERVER1 80host1/Admin(config-sfarm-host-rs)#To remove the real server association with the server farm, enter:
host1/Admin(config-sfarm-host)# no rserver SERVER1 80After you have associated a real server with a server farm, you can configure other real server attributes as described in the following topics:
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Configuring the Weight of a Real Server in a Server Farm
The ACE uses a real server weight value with the weighted round-robin and least connections predictor methods. Servers with higher weight values receive a proportionally higher number of connections than servers with lower weight values. If you do not specify a weight in real configuration mode under a server farm, the ACE uses the weight you configured for the global real server in real server configuration mode. See the "Configuring a Real Server Weight" section.
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You can configure the weight of a real server in a server farm by using the weight command in server farm host real server configuration mode. The syntax of this command is as follows:
weight number
The number argument is the weight value assigned to a real server in a server farm. Enter an integer from 0 to 100. The default is 8.
For example, enter:
host1/Admin(config-sfarm-host-rs)# weight 50To reset the configured weight of a real server to the default of 8, enter:
host1/Admin(config-sfarm-host-rs)# no weightConfiguring a Backup Server for a Real Server
You can designate an existing real server as a backup server for another real server in case that server becomes unavailable. A backup server is sometimes referred to as a sorry server. If the real server becomes unavailable, the ACE automatically redirects client requests to the backup server. You can configure a backup server by using the backup-rserver command in server farm host real server configuration mode.
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The syntax of this command is as follows:
backup-rserver name [port]
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For example, enter:
host1/Admin(config-sfarm-host-rs)# backup-rserver SERVER1 4000To remove the backup server from the configuration, enter:
host1/Admin(config-sfarm-host-rs)# no backup-rserverConfiguring Health Monitoring for a Server Farm
You can monitor the health of the real servers in a server farm by configuring one or more health probes (sometimes called keepalives) for the server farm. You can associate multiple probes of the same or different protocols with a server farm. Once you configure the probes, the ACE periodically sends the probes to the real servers. If the ACE receives the appropriate responses from the servers, the ACE includes the servers in load-balancing decisions. If not, the ACE marks the servers as out of service, depending on the configured number of retries.
You can associate a health probe with a server farm by using the probe command in server farm host real server configuration mode. The syntax of this command is as follows:
probe probe_name
For the probe_name argument, enter the name of an existing probe as an unquoted text string with no spaces and a maximum of 64 alphanumeric characters.
For example, enter:
host1/Admin(config-sfarm-host-rs)# probe PROBE1_TCPTo remove the real server health probe from the configuration, enter:
host1/Admin(config-sfarm-host-rs)# no probe PROBE1_TCPConfiguring Connection Limits for a Real Server in a Server Farm
You can prevent a real server from becoming overloaded by limiting the number of connections allowed to that server. You can limit the number of connections to a real server by using the conn-limit command in server-farm real server configuration mode. The syntax of this command is as follows:
conn-limit max maxconns min minconns
The keywords and arguments are as follows:
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Because the ACE has two network processors (NPs), the maxconns value for a real server is divided between the two NPs. If you configure an odd value for maxconns, one of the NPs will have a maxconns value that is one greater than the value on the other NP. With very small values for maxconns, it is possible for a connection to be denied, even though one of the NPs has the capacity to handle the connection.
Consider the scenario where you configure a value of 3 for the maxconns argument for a real server. One NP will have a value of 2 and the other NP will have a value of 1. If both NPs have reached their connection limits for that server, the next connection request for that server will be denied and the Out-of-rotation Count field of the show serverfarm detail command will increment by 1. Now, suppose a connection is closed on the NP with the maxconns value of 2. If the next connection request to the ACE goes to the NP with the maxconns value of 1 and it has already reached its limit, the ACE denies the connection, even though the other NP has the capacity to service the connection.
For example, enter:
host1/Admin(config-sfarm-host-rs)# conn-limit max 5000 min 4000To remove the connection limit from a real server, enter:
host1/Admin(config-sfarm-host-rs)# no conn-limitPlacing a Real Server in Service
Before you can start sending connections to a real server in a server farm, you must place it in service. You can place a real server in a server farm in service by using the inservice command in either server farm host real server or server farm redirect real server configuration mode.
The syntax of this command is as follows:
inservice [standby]
Use the optional standby keyword when you are configuring backup real servers. The standby keyword specifies that a backup real server remain inactive unless the primary real server fails. If the primary fails, the backup server becomes active and starts accepting connections.
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For example, enter:
host1/Admin(config-sfarm-host-rs)# inservice standbyTo take a backup real server out of service for maintenance or software upgrades, enter:
host1/Admin(config-sfarm-host-rs)# no inservice standbyGracefully Shutting Down a Server with Sticky Connections
In addition to putting a backup real server in service standby, another use of the inservice standby command is to provide a graceful shutdown of primary real servers. Use this command to gracefully shut down servers with sticky connections. When you enter this command for a primary real server, the ACE does the following:
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For example, to perform a graceful shutdown on a primary real server with sticky connections in a server farm, enter:
host1/Admin(config)# serverfarm sf1host1/Admin(config-sfarm-host)# rserver rs1host1/Admin(config-sfarm-host-rs)# inservice standbyConfiguring a Backup Server Farm
Configure a backup server farm to ensure that, if all the real servers in a server farm go down, the ACE continues to service client requests. You configure a backup server farm as an action in a Layer 7 policy map under a Layer 7 class map using the serverfarm name1 [backup name2 [sticky] [aggregate-state]] command. For details about configuring a backup server farm, see the "Enabling Load Balancing to a Server Farm (Configuring a Backup Server)" section in Chapter 3, Configuring Traffic Policies for Server Load Balancing.
Specifying No NAT
You can instruct the ACE not to use NAT to translate the VIP address to the server IP address by using the transparent command in serverfarm host configuration mode. Use this command in firewall load balancing (FWLB) when you configure the insecure and secure sides of the firewall as a server farm. For details about FWLB, see Chapter 6, Configuring Firewall Load Balancing. The syntax of this command is as follows:
transparent
For example, enter:
host1/Admin(config-sfarm-host)# transparentDisplaying Real Server Configurations and Statistics
This section describes the commands that you can use to display information about the real-server configuration and statistics. It contains the following topics:
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Displaying Real Server Configurations
You can display information about the real-server configuration by using the show running-config rserver command in Exec mode. The syntax of this command is as follows:
show running-config rserver
Displaying Real Server Statistics
You can display summary or detailed statistics for a named real server or for all real servers by using the show rserver command in Exec mode. The syntax of this command is as follows:
show rserver [name] [detail]
The argument and option are as follows:
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For example, to display detailed statistics for all configured real servers, enter:
host1/Admin# show rserver detailTable 2-3 describes the fields in the show rserver command output.
Displaying Real Server Connections
You can display active inbound and outbound real server connections by using the show conn rserver command in Exec mode. The syntax of this command is as follows:
show conn rserver name1 [port_number] [name2]
The arguments of this command are as follows:
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For example, enter:
host1/Admin# show conn rserver SERVER1 4000 serverfarm SFARM1Table 2-4 describes the fields in the show conn rserver command output.
Clearing Real Server Statistics and Connections
This section describes the commands you use to clear real server statistics and connection information. It contains the following topics:
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Clearing Real Server Statistics
You can reset statistics to zero for all instances of a particular real server regardless of the server farms that it is associated with by using the clear rserver command in Exec mode. The syntax of this command is as follows:
clear rserver name
The name argument is the identifier of an existing real server whose statistics you want to clear. Enter a real server name as an unquoted text string with no spaces and a maximum of 64 alphanumeric characters.
For example, to reset the statistics of real server SERVER1, enter:
host1/Admin# clear rserver SERVER1
Note
Clearing Real Server Connections
You can clear real server connections by using the clear conn rserver command in Exec mode. The syntax of this command is as follows:
clear conn rserver name1 [port] serverfarm name2
The arguments and keyword are as follows:
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For example, enter:
host1/Admin# clear conn rserver SERVER1 4000 SFARM1Displaying Server Farm Configurations and Statistics
This section describes the commands that you can use to display server farm configurational and statistical information. It contains the following topics:
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Displaying Server Farm Configurations
You can display information about the server farm configuration by using the show running-config serverfarm command in Exec mode. The syntax of this command is as follows:
show running-config serverfarm
Displaying Server Farm Statistics
You can display summary or detailed server-farm statistics by using the show serverfarm command in Exec mode. The syntax of this command is as follows:
show serverfarm [name [detail | retcode]]
The argument and option are as follows:
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For example, enter:
host1/Admin# show serverfarm name sfarm1 detailTable 2-5 describes the fields in the show serverfarm detail command output.
Table 2-5 Field Descriptions for the show serverfarm detail Command
OutputServerfarm
Name of the server farm.
Type
Configured server farm type: HOST or REDIRECT.
Total Rservers
Total number of real servers associated with a real server.
Description
User-entered text description of the server farm with a maximum of 240 alphanumeric characters.
Predictor
Configured load-balancing method. Possible values are as follows:
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Failaction
Action that the ACE takes for connections if a real server fails in a server farm. Possible actions are purge or none.
Total Conn-dropcount
Total number of connections that the ACE discarded because the number of connections exceeded the configured conn-limit max value. See the "Configuring Real Server Connection Limits" section.
Real
Rserver
Name of the real server associated with the server farm.
IP Address:Port
IP address and port of the real server.
Weight
Weight assigned to the real server in the server farm.
State
Current state of the real server. Possible states are OPERATIONAL or OUTOFSERVICE.
Current Connections
Number of active connections to the real server.
Total Connections
Total number of connections to the specified server farm.
Maxconns
Configured maximum allowable number of active connections to a real server.
Minconns
Configured minimum number of connections that the number of connections must fall below before sending more connections to a server after it has exceeded the maximum connections threshold.
Total Conn-failures
Total number of connection attempts that failed to establish a connection to the real server.
NP
Number of the network processor (1 or 2) associated with the return codes.
Return Code
Number of the return code.
Action
Configured action for the return code, Count only.
Total Count
Total number of times that the ACE encountered the return code in network traffic and counted the return code.
Displaying Server Farm Connections
You can display the current active inbound and outbound connections for all real servers in a server farm by using the show conn serverfarm command in Exec mode. The syntax of this command is as follows:
show conn serverfarm name
The name argument is the name of the server farm whose real-server connections you want to display. Enter an unquoted alphanumeric text string with no spaces and a maximum of 64 alphanumeric characters.
For example, enter:
host1/Admin# show conn serverfarm sfarm1
Table 2-6 describes the fields in the show conn serverfarm command output.
Clearing Server Farm Statistics
You can reset statistics to zero for all real servers in a specified server farm by using the clear serverfarm command in Exec mode. The syntax of this command is as follows:
clear serverfarm name
The name argument is the identifier of an existing server farm whose real server statistics you want to clear. Enter a server farm name as an unquoted text string with no spaces and a maximum of 64 alphanumeric characters.
For example, to reset the statistics of all real servers in server farm SF1, enter:
host1/Admin# clear serverfarm SF1
Note
Where to Go Next
Once you are satisfied with your real server and server-farm configurations, configure an SLB traffic policy to filter interesting traffic and load balance it to the servers in your server farm, as described in Chapter 3, Configuring Traffic Policies for Server Load Balancing.
