8-4
User
Guide

for

the

Cisco

Application

Networking

Manager

5.2
OL-26572-01
Chapter
8






Configuring

Real

Servers

and

Server

Farms
Information
About

Server

Load

Balancing
weighted
round-robin

and

the

least-connections

load-balancing

predictors.

The

load-balancing

predictor
algorithms
(for

example,

roundrobin,

least

connections,

and

so

on)

determine

the

servers

to

which

the
ACE
sends

connection

requests.

For

a

listing

and

brief

description

of

the

load-balancing

predictors,

see
the
“Load-Balancing

Predictors”

section

on

page

8-2 .
The
ACE

uses

traffic

classification

maps

(class

maps)

within

policy

maps

to

identify

traffic

that

meets
defined
criteria

and

to

apply

specific

actions

to

that

traffic

based

on

the

SLB

configuration.
If
a

primary

real

server

fails,

t

he

ACE

t

akes

t

hat

server

out


of

ser

vice

and

no

longer

i

ncludes

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

Virtual

Server

Layer

7

Load

Balancing”

section

on

pa

ge

7-30 .
The
ACE

can

take

a

re

al

server

out


of

ser

vice

for


the

fol

lowing

reasons:

•
Probe
failure

•
ARP
timeout

•
Neighbor
Discovery

(ND)
failure
(IPv6

only,
which
requires

ACE

module

and

ACE

appliance
software
Version

A5(1.0)

or

l

ater)

•
Specifying
Out
Of

Service

as

the

administrative

state

of

a

real

server

•
Specifying
Inservice

Standby

as

the

administrative

state

of

a

real

server
The
Out

Of

Service

and

Inservice

Standby

selections

both

provide

the

graceful

shutdown

of

a

server.
Related
Topics

•
Configuring
Real
Servers,
page
8-5

•
Configuring
Health
Monitoring
for
Real

Servers,

page
8-51
Dynamic
Workload

Scaling

Overview
Note
Dynamic
Workload

Scaling

requires

ACE

module

or

appliance

software

Version

A4(2.0)

or

later

and

a
pair
of

the

Cisco

Nexus

7000

Ser

ies

switches

with

Overlay

Transport

Virtualization

(OTV)

technology.
The
ACE

Dynamic

Workload

Scaling

(DWS)

feature

per

mits

on-

demand

access

t

o

remote

resources,
such
as

VMs,

that

you

own

or

l

ease

from

an

Int

ernet

ser

vice

provider

or

cl

oud

service

provider.

This
feature
uses

Cisco

Nexus

7000

Series

switches

with

OTV

to

create

a

Data

Center

Interconnect

(DCI)

on
a
Layer

2

l

ink

over

an

existing

IP

network

between

geographically

di

stributed

data

centers

(see
Figure
1-1 ).

The

local

data

center

Cisco

Nexus

7000

Series

switch

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

for

DWS,

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

VMs

(local

or
remote).
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
and/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

local

VM

usage

drops
below
its

configured

minimum

threshold

value.