Table Of Contents
Configuring Server Load Balancing
Information About Server Load Balancing
Configuring Server Load Balancing
Task Flow for Configuring Server Load Balancing
Configuring Real Servers
Creating a Server Farm
Creating a Virtual Server Traffic Policy
Configuration Example for Configuring Server Load Balancing
Where to Go Next
Configuring Server Load Balancing
This chapter describes how to configure server load balancing (SLB) on the Cisco Application Control Engine (ACE) module.
This chapter contains the following sections:
•
Information About Server Load Balancing
•Configuring Server Load Balancing
•Configuration Example for Configuring Server Load Balancing
•Where to Go Next
Information About Server Load Balancing
After reading this chapter, you should have an understanding of the basic SLB capabilities provided by the ACE. You should also be able to configure a virtual server for Layer 7 load-balancing purposes.
When there is a client request for web services, a load-balancing device decides to which server it should send the request. For example, a client request may consist of an HTTP GET for a web page or an FTP GET to download a file. The ACE, as a server load balancer, selects a server that can successfully fulfill the client request in the shortest amount of time without overloading either the server or the server farm as a whole.
The ACE uses a virtual server to intercept web traffic to a website. A virtual server allows multiple real servers to appear as one for load-balancing purposes. A virtual server, also called a Virtual IP (VIP), is defined by its IP address, the protocol used (for example, UDP or TCP), and the port address.
Multiple servers grouped together in server farms are assigned to each virtual server and the ACE carries out load balancing across them. Real servers are dedicated servers that provide services to clients—for example, delivery of HTTP or XML content. Real servers within a server farm usually contain the same content and typically reside in the same physical location in a data center.
This chapter describes how to configure a virtual serverusing the network example in Figure 6-1.
Figure 6-1 Example Server Load-Balancing Setup
The configuration of the example setup is as follows:
•A virtual server VS_WEB is created with a virtual IP address 10.10.40.10 to forward the client traffic from VLAN 400 to the application servers in VLAN 500.
•There are four real servers grouped into the server farm SF_WEB.
•The virtual server uses a round-robin predictor to forward the client requests to one of the real servers in the server farm.
Configuring Server Load Balancing
This section describes how to configure server load balancing. It contains the following topics:
•Task Flow for Configuring Server Load Balancing
•Configuring Real Servers
•Creating a Server Farm
•Creating a Virtual Server Traffic Policy
Task Flow for Configuring Server Load Balancing
Follow these steps to configure server load balancing:
Step 1 Configure real servers.
Step 2 Create a server farm.
Step 3 Create a virtual server traffic policy.
Configuring Real Servers
Procedure
| |
Command
|
Purpose
|
Step 1
|
Example:
host1/Admin# changeto VC_WEB
|
Changes to the correct context if necessary. Check the CLI prompt to verify that you are operating in the desired context.
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Step 2
|
Example:
|
Enters configuration mode.
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Step 3
|
rserver name
Example:
host1/VC_WEB(config)# rserver RS_WEB1
host1/VC_WEB(config-rserver-host)#
|
Creates a real server named RS_WEB1 as type host (the default).
|
Step 4
|
description string
Example:
host1/VC_WEB(config-rserver-host)#
description content server web-one
|
Enters a description of the real server.
|
Step 5
|
ip address address
Example:
host1/VC_WEB(config-rserver-host)# ip
address 10.10.50.10
|
Assigns the real server with an IP address of 10.10.50.10.
|
Step 6
|
inservice
Example:
host1/VC_WEB(config-rserver-host)#
inservice
|
Places the real server in service.
|
Step 7
|
exit
Example:
host1/VC_WEB(config-rserver-host)# exit
host1/VC_WEB(config)#
|
Exits real server host configuration mode.
|
Step 8
|
rserver name
Example:
host1/VC_WEB(config)# rserver RS_WEB2
host1/VC_WEB(config-rserver-host)#
|
Add three more real servers by repeating Steps 3 through 7, using the following real server names, descriptions, and IP addresses.
For RS_WEB2, enter:
•Name: RS_WEB2
•Description: content server web-two
•IP Address: 10.10.50.11
For RS_WEB3, enter:
•Name: RS_WEB3
•Description: content server web-three
•IP Address: 10.10.50.12
For RS_WEB4, enter:
•Name: RS_WEB4
•Description: content server web-four
IP Address: 10.10.50.13
|
description string
Example:
host1/VC_WEB(config-rserver-host)#
description content server web-two
|
ip address address
Example:
host1/VC_WEB(config-rserver-host)# ip
address 10.10.50.11
|
inservice
Example:
host1/VC_WEB(config-rserver-host)#
inservice
|
|
Example:
host1/VC_WEB(config-rserver-host)# exit
|
Step 9
|
do show running-config rserver
Example:
host1/VC_WEB(config)# do show
running-config rserver
|
Displays the configuration of the real servers.
|
Step 10
|
do copy running-config startup-config
Example:
host1/Admin(config)# do copy
running-config startup-config
|
(Optional) Copies the running configuration to the startup configuration.
|
Creating a Server Farm
After you create and configure the real servers, you can create a server farm and associate the real servers with it.
Procedure
| |
Command
|
Purpose
|
Step 1
|
serverfarm name
Example:
host1/VC_WEB(config)# serverfarm SF_WEB
host1/VC_WEB(config-sfarm-host)#
|
Creates a server farm of type host (the default) named SF_WEB.
|
Step 2
|
rserver name [port]
Example:
host1/VC_WEB(config-sfarm-host)#
rserver RS_WEB1 80
host1/VC_WEB(config-sfarm-host-rs)#
|
Associates real server RS_WEB1 with the server farm through port 80. Specifying a port number is optional. If you do not specify a port number, the ACE does not perform PAT and the destination port that was used from the client to the VIP will also be used from the VIP to the real server. When you specify a port number, it is the only destination port that the ACE uses from the VIP to the real server.
|
Step 3
|
inservice
Example:
host1/VC_WEB(config-sfarm-host-rs)#
inservice
|
Places the real server in service within the server farm.
Note Before you can start sending connections to a real server in a server farm, you must place it in service. Otherwise, the ACE considers it out of service and the server farm cannot receive or respond to client requests.
|
Step 4
|
exit
Example:
host1/VC_WEB(config-sfarm-host-rs)#
exit
host1/VC_WEB(config-sfarm-host)#
|
Exits server farm host real server configuration mode.
|
Step 5
|
rserver name [port]
inservice
Example:
host1/VC_WEB(config-sfarm-host)#
rserver RS_WEB2 80
host1/VC_WEB(config-sfarm-host-rs)#
inservice
host1/VC_WEB(config-sfarm-host-rs)#
exit
host1/VC_WEB(config-sfarm-host)#
rserver RS_WEB3 80
host1/VC_WEB(config-sfarm-host-rs)#
inservice
host1/VC_WEB(config-sfarm-host-rs)#
exit
host1/VC_WEB(config-sfarm-host)#
rserver RS_WEB4 80
host1/VC_WEB(config-sfarm-host-rs)#
inservice
host1/VC_WEB(config-sfarm-host-rs)#
exit
|
Similarly, associates the RS_WEB2, RS_WEB3, and RS_WEB4 real servers with the SF_WEB server farm and places the real server in service. Repeat steps 2 through 4 to configure the remaining real servers in the server farm.
|
Step 6
|
exit
Example:
host1/VC_WEB(config-sfarm-host)# exit
|
Exits server farm host configuration mode.
|
Step 7
|
Example:
host1/VC_WEB(config)# do show rserver
RS_WEB1
host1/VC_WEB(config)# do show rserver
RS_WEB2
host1/VC_WEB(config)# do show rserver
RS_WEB3
host1/VC_WEB(config)# do show rserver
RS_WEB4
|
Displays the information for the real servers.
Note The real server status is shown as ARP_FAILED because network connectivity has not been established yet.
|
Step 8
|
do copy running-config startup-config
Example:
host1/VC_WEB(config)# do copy
running-config startup-config
|
(Optional) Copies the running configuration to the startup configuration.
|
Creating a Virtual Server Traffic Policy
Procedure
| |
Command
|
Purpose
|
Step 1
|
policy-map type loadbalance first-match
name
Example:
host1/VC_WEB(config)# policy-map type
loadbalance first-match PM_LB
host1/VC_WEB(config-pmap-lb)#
|
Creates a Layer 7 server load-balancing policy map named PM_LB to match the class maps in the order in which they occur for load balancing.
Note The ACE uses a class map to specify a series of flow match criteria (traffic classifications). The ACE uses a policy map to define a series of actions (functions) that you want applied to a set of classified inbound traffic.
|
Step 2
|
class class-default
Example:
host1/VC_WEB(config-pmap-lb)# class
class-default
host1/VC_WEB(config-pmap-lb-c)#
|
For a simple load-balancing policy, assigns the ACE default class map which contains an implicit match any statement to match any traffic classification.
|
Step 3
|
serverfarm name
Example:
host1/VC_WEB(config-pmap-lb-c)#
serverfarm SF_WEB
|
Adds the server farm SF_WEB to the Layer 7 server load-balancing policy map and exits configuration mode.
|
Step 4
|
exit
Example:
host1/VC_WEB(config-pmap-c)# exit
host1/VC_WEB(config-pmap)# exit
host1/VC_WEB(config)#
|
Exits policy map class configuration mode. Exits policy map configuration mode.
|
Step 5
|
class-map {match-all| match-any | type}
name
Example:
host1/VC_WEB(config)# class-map VS_WEB
host1/VC_WEB(config-cmap)#
|
Creates a Layer 3 and Layer 4 load-balancing class map VS_WEB. The default is match-all.
|
Step 6
|
match virtual-address address netmask
tcp eq port
Example:
host1/VC_WEB(config-cmap)# match
virtual-address 10.10.40.10
255.255.255.255 tcp eq 80
|
Defines a match statement for the IP address 10.10.40.10, the TCP IP protocol, and port 80.
|
Step 7
|
exit
Example:
host1/VC_WEB(config-cmap)# exit
host1/VC_WEB(config)#
|
Exits class map configuration mode.
|
Step 8
|
policy-map multi-match name
Example:
host1/VC_WEB(config)# policy-map
multi-match PM_MULTI_MATCH
host1/VC_WEB(config-pmap)#
|
Creates a Layer 3 and Layer 4 multi-match policy map to direct classified incoming requests to the load-balancing policy map.
|
Step 9
|
class name
Example:
host1/VC_WEB(config-pmap)# class VS_WEB
host1/VC_WEB(config-pmap-c)#
|
Associates the VS_WEB Layer 3 and Layer 4 class map that you created in Step 4 with the PM_MULTI_MATCH policy map.
|
Step 10
|
loadbalance policy name
Example:
host1/VC_WEB(config-pmap-c)#
loadbalance policy PM_LB
host1/VC_WEB(config-pmap-lb-c)#
|
Associates the PM_LB Layer 7 load-balancing policy map with the PM_MULTI_MATCH Layer 3 and Layer 4 policy map.
|
Step 11
|
loadbalance vip inservice
Example:
host1/VC_WEB(config-pmap-lb-c)#
loadbalance vip inservice
|
Enables a VIP for load-balancing operations.
|
Step 12
|
exit
Example:
host1/VC_WEB(config-pmap-c)# exit
host1/VC_WEB(config-pmap)# exit
host1/VC_WEB(config)#
|
Exits policy map class configuration mode. Exits policy map configuration mode.
|
Step 13
|
interface vlan vlan_id
Example:
host1/VC_WEB(config)# interface vlan
400
|
Accesses the interface to which you want to apply the multi-match policy map.
|
Step 14
|
service-policy input policy_name
Example:
host1/VC_WEB(config-if)# service-policy
input PM_MULTI_MATCH
|
Applies the PM_MULTI_MATCH Layer 3 and Layer 4 policy map.
|
Step 15
|
exit
Example:
host1/VC_WEB(config-if)# exit
host1/VC_WEB(config)# exit
|
Exits interface configuration mode. Exits configuration mode.
|
Step 16
|
show service-policy policy_name
Example:
host1/VC_WEB# show service-policy
PM_MULTI_MATCH
|
Displays the service policy state for the PM_MULTI_MATCH policy map.
|
Step 17
|
copy running-config startup-config
Example:
host1/VC_WEB# copy running-config
startup-config
|
(Optional) Copies the running configuration to the startup configuration.
|
Configuration Example for Configuring Server Load Balancing
The following example shows how to configure server load balancing. The commands that you have configured in this chapter appear in bold text.
switch/VC_WEB(config)# do show running config
Generating configuration....
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
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
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
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
DOMAIN1
Where to Go Next
In this chapter, you have configured real servers, a server farm, and a a virtual server for load-balancing HTTP traffic. In the next chapter, you will configure a load-balancing predictor to forward client requests to the appropriate real servers.
