Cisco Explorer 4700 Installation Guide download pdf (Page 206)

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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

Server Load Balancing Overview

The ACE appliance 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.

If a primary real server fails, the ACE appliance 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

appliance redirects the primary real server connections to the backup server. For information about

configuring a backup server, see the Configuring Virtual Server Layer 7 Load Balancing, page 5-30.

The ACE appliance can take a real server out of service for the following reasons:

• Probe failure

• ARP timeout

• Neighbor Discovery (ND) failure (IPv6 only)

• Retcode failure

• Reaching the maximum number of connections

• Specifying Out Of Service as the administrative state of a real server

• Specifying In Service Standby as the administrative state of a real server

The Out Of Service and In Service Standby selections both provide the graceful shutdown of a server.

Related Topics

• Configuring Real Servers, page 6-5

• Configuring Health Monitoring for Real Servers, page 6-41

Dynamic Workload Scaling Overview

The ACE Dynamic Workload Scaling feature permits on-demand access to remote resources, such as

VMs, that you own or lease from an Internet service provider or cloud service provider. This feature uses

Cisco Nexus 7000 Series switches with Overlay Transport Virtualization (OTV) technology to create a

Data Center Interconnect (DCI) on a Layer 2 link over an existing IP network between geographically

distributed data centers. The local data center Nexus 7000 contains an OTV forwarding table that lists

the MAC addresses of the Layer 2 extended virtual private network (VPN) and identifies the addresses

as either local or remote.

When you configure the ACE to use this feature, the ACE uses an XML query to poll the Cisco Nexus

7000 Series Switch and obtain the OTV forwarding table information to determine the locality of the

local or remote VMs. The ACE also uses a health monitor probe that it sends to the local VMware

vCenter Server to monitor the load of the local VMs based on CPU usage, memory usage, or both. When

the average CPU or memory usage of the local VMs reaches its configured maximum threshold value,

the ACE bursts traffic to the remote VMs. The ACE stops bursting traffic to the remote VMs when the

average CPU or memory usage of the local VMs drops below its configured minimum threshold value.

To use Dynamic Workload Scaling, you configure the ACE to connect to the Data Center Interconnect

device (Cisco Nexus 7000 Series switch) and the VMware Controller associated with the local and

remote VMs. You also configure the ACE with the probe type VM to monitor a server farm’s local VM

CPU and memory usage, which determines when the ACE bursts traffic to the remote VMs.

For more details on this feature, see the Server Load-Balancing Guide, Cisco ACE Application Control

Engine.

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