8-44

User

Guide

for

the

Cisco

Application

Networking

Manager

5.2

OL-26572-01

Chapter

8

Configuring

Real

Servers

and

Server

Farms

Configuring

Server

Farms

Least

Lo

aded

Least

l

oaded

server

based

on

information

from

SNMP

probes.

Do

the

fol

lowing:

a.

In

the

SNMP

Probe

Name

field,

choose

the

name

of

the

SNMP

probe

to

use.

b.

In

the

Auto

Adjust

field,

configure

the

autoadjust

feature

to

instruct

the

ACE

to

apply

the

maximum

load

of

16000

to

a

real

server

whose

load

reaches

zero

or

override

the

default

behavior.

By

default,

the

ACE

applies

the

average

load

of

the

server

farm

to

a

real

server

whose

load

is

zero.

The

ACE

periodically

adjusts

this

load

value

based

on

feedback

from

the

server

SNMP

probe

and

other

configured

options.

Options

include

the

following:

–

Average—Instructs

the

ACE

to

apply

the

average

load

of

the

server

farm

to

a

real

server

whose

load

is

zero.

This

setting

allows

the

server

to

participate

in

load

balancing,

while

preventing

it

from

being

flooded

by

new

connections.

This

is

the

default

setting.

–

Maxload—Instructs

the

ACE

to

apply

the

maximum

load

of

the

server

farm

to

a

real

server

whose

load

reaches

zero.

The

maxload

option

requires

the

following

ACE

software

versions:

-

ACE

appliance—A3(2.7)

or

A4(1.0)

or

later

-

ACE

module—A2(2.4),

A2(3.2),

or

A4(1.0)

or

l

ater

If

you

choose

the

maxload

option

and

the

ACE

does

not

support

the

option,

ANM

issues

a

command

parse

error

message.

–

Off—Instructs

the

ACE

to

send

all

new

connections

to

the

server

that

has

a

load

of

zero

until

the

next

load

update

arrives

from

t

he

SNMP

pr

obe

for

this

ser

ver.

There

may

be

times

when

you

want

the

ACE

to

send

all

new

connections

to

a

real

server

whose

load

is

zero.

c.

In

th

e

Weight

Connection

field,

check

th

e

ch

eck

box

to

i

nstruct

th

e

ACE

to

use

t

he

c

urrent

connection

count

in

the

final

load

calculation

for

a

real

server.

When

you

configure

this

option,

the

ACE

includes

the

current

connection

count

in

the

total

load

calculation

for

each

real

server

in

a

server

farm.

Uncheck

the

check

box

to

reset

the

behavior

of

the

ACE

to

the

default

of

excluding

the

current

connection

count

from

the

load

calculation.

To

instruct

the

ACE

to

select

the

server

with

the

lowest

load,

use

the

predictor

least-loaded

command

in

server

farm

host

or

redirect

configuration

mode.

With

this

predictor,

the

ACE

uses

SNMP

probes

to

query

the

real

servers

for

load

parameter

values

(for

example,

CPU

utilization

or

memory

utilization).

This

predictor

i

s

considered

adaptive

because

the

ACE

continuously

provides

feedback

to

t

he

load-balancing

algorithm

based

on

the

behavior

of

the

real

server.

To

use

this

predictor,

you

must

associate

an

SNMP

probe

with

it.

The

ACE

queries

user-specified

OIDs

periodically

based

on

a

configurable

time

interval.

The

ACE

uses

the

retrieved

SNMP

load

value

to

determine

the

server

with

the

lowest

load.

The

syntax

of

this

predictor

command

is

as

follows:

predictor

least-loaded

probe

name

The

name

argument

specifies

the

identifier

of

the

existing

SNMP

probe

that

you

want

the

ACE

to

use

to

query

the

server.

Enter

an

unquoted

text

string

with

no

spaces

and

a

maximum

of

64

alphanumeric

characters.

Table

8-9

Predictor

Method

Attributes

(continued)

Predictor

Method

Description

/

Action