ETH202: Introduction to Web Switching and Load BalancingServerIron ADX(config-rs-R5)# server virtual-name VIP1 198.10.10.100 ServerIron ADX(config-vs-VIP1)# port http lb-pri-servers

Introduction to ServerIron ADX Application

Switching and Load Balancing

Module 5: Server Load Balancing (SLB)

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Objectives

Upon completion of this module the student will be able to:

– Describe Source-NAT

– Describe Hot Standby Redundancy

– Define Direct Server Return (DSR)

– Define Active Standby Redundancy

– Define Remote Servers

– Describe Primary and Backups

Source-NAT

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The Problem: ServerIron ADX in a Multinetted

Network Without Source-NAT

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The Solution: ServerIron ADX in a Multinetted

Network With Source-NAT

ServerIron ADX can operate in a multinetted environment

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Source NAT configured on a per real server basis (local)

• Source NAT under individual real server‟s is recommended

Source NAT can be configured on a global level

Source-NAT Example

server source-nat

server source-ip 10.10.10.50 255.255.255.0 10.1.1.1

!

server real rs1 10.10.10.201

source-nat

port http

port http url “HEAD /”

!

server real rs2 10.10.10.202

source-nat

port http

port http url “HEAD /”

!

server virtual vip 169.144.10.100

port http

bind http rs1 http rs2 http

bind http rs4 http

Use Source-NAT to reach these servers

Source-NAT

Lab 5-1

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Lab 5-1:Source NAT

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Lab 5-1 Review: Source-NAT Packet Walk

Hot-Standby Redundancy

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Hot-Standby Redundancy (1 of 3)

Dedicated Synchronization Link

– State tables are synchronized through this link without using bandwidth on the data path

– Detects failure of the “Active” switch within 1 sec

– In the event of a Sync Link failure, the data path is checked to see if the “Active” switch is still online

Requires a common Layer 2 Domain:

– Switches & Real Servers

Traffic is “heard” by both Switches

– “Active” Switch switches traffic from clients to the appropriate Physical Servers

– “Standby” Switch also builds Network Address Translation (NAT) table, but passes no traffic while in Standby-mode

Both Switches are configured with the same MAC address (One or the other switch‟s lowest MAC)

– When the “Standby” takes over, no re-ARP is needed

– Client community still uses mapping of Virtual IP to locally administered MAC address being advertised

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Hot-Standby Redundancy (2 of 3)

When an “Active” Switch fails…

– Standby switch listens through

sync link to detect when the

other side is no longer alive

– Session information is kept in

sync until the “Active” fails to

communicate with the “Standby”

– Data path is also checked (via

ping) to see if it was merely a

failure in the Sync link

“Standby” switch becomes “Active”

Client to server connections are preserved across

the “Active” to “Standby” failover

Any lost packet retries are re-initiated by the

client/server

No re-ARPing is required by clients or downstream

routers

– Both switches are configured with the same

Locally Administered Address (LAA) MAC

e.g. 02-00-0c-76-d8-88

During the failure, the “Standby” switch now

operates as the “Active” switch and switches traffic

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Hot-Standby Redundancy (3 of 3)

The failed switch can be swapped out and replaced while server

farm is operational

– The new switch takes the “Standby” role upon detection of the

“Active” switch

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On both ADX’s:

ADX(config)# server backup ethernet 1 00e0.5202.85ae

ADX(config-vlan-22)# no spanning-tree

This is the port that the

„heart beat‟ cable is connected to.

This is a MAC address of port one on one of the

ServerIron ADXs. Enter this SAME MAC address on both

ServerIron ADXs. Use the command “show interface brief”

to display the MAC addresses.

Hot-Standby Redundancy Configuration

ADX(config)# server backup-preference 5

The ServerIron ADX with this command will always be the active ServerIron ADX. The 5 is the time it will take

for the this ServerIron ADX to become active again in minutes, 5 is the minimum value.

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Synchronization of Configurations

Configuration ServerIron ADX A:

ServerIron ADXA# configure terminal

ServerIron ADXA(config)# config-sync sender e 1 mac 00e0.5201.0c72 vlan 22

Configuration ServerIron ADX B:

ServerIron ADXB# configure terminal

ServerIron ADXB(config)# config-sync receiver e 1 mac 00e0.5202.020a vlan 22

Initiating and and Ending the Synchronization:

ServerIron ADXA(config)# confic-sync slb

Hot-Standby Redundancy

Lab 5-2

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Lab 5-2: Hot-Standby Redundancy

Direct Server Return (DSR)

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Direct Server Return (DSR) Overview

Responses from the Real Servers are sent directly back to clients

via the router

Optimal for high-bandwidth, low latency SLB applications

Traffic Flow: a. Small requests are sent from client to the Server Farm (typically 64-128 byte)

b. The small requests can result in large frames being sent directly back to the client

– Large GIF/JPEG images – Large File transfers – Maximize the throughput back to the users

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DSR Configuration

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DSR in Action

Direct Server Return (DSR)

Lab 5-3

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Lab 5-3: Direct Server Return (DSR)

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Lab 5-3 Review: DSR Packet Walk

Active-Standby Redundancy

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Symmetric Server Load Balancing Active-Standby

Dual ADXs share active loads

Both ADXs are “Active” and continue to be a “backup” for each other in

case the other fails

Supports more connections, more throughput

Same application/port cannot be mapped to 2 or more VIPs

– If necessary create an alias port

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Active-Standby SLB

server virtual vip2 169.144.10.200

• port http

• bind http RS1 2000 RS2 2000

• no port http translate

server virtual vip1 169.144.10.100

• port http

• bind http RS1 http RS2 http

Steps to configure VIP 1 and VIP 2 on both ADX-A and ADX-B

Active-Standby Redundancy

Lab 5-4

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Lab 5-4: Active-Standby Redundancy

Remote Server

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Remote Server Farms

Remote Server Farms can be:

– on a different subnet

– located in a different facility (disaster recovery)

– used as BACKUP of last resort (i.e. used only if all of the Local Servers are unavailable)

– specify Source-NAT so the traffic back to the client appears to have returned from the

VIP

– cannot configure DSR on a remote server

Remote Server

Lab 5-5

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Lab 5-5:Remote Server

Other Features

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Active-Active Symmetric Server Load Balancing

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Primary and Backup Servers

Primary/Backup – Local or Remote

Servers that are locally attached to the ServerIron ADX (not separated by one or

more router hops) are local servers.

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Primary/Backup Server Configuration Example

ServerIron ADX(config)# server real-name R3 10.10.10.203

ServerIron ADX(config-rs-R3)# backup

ServerIron ADX(config-rs-R3)# port http

ServerIron ADX(config-rs-R3)# exit

ServerIron ADX(config)# server remote-name R5 198.10.10.50

ServerIron ADX(config-rs-R5)# backup

ServerIron ADX(config-rs-R5)# port http

ServerIron ADX(config)# server real-name R1 10.10.10.201

ServerIron ADX(config-rs-R1)# port http

ServerIron ADX(config-rs-R1)# exit

ServerIron ADX(config)# server remote-name R4 198.10.10.40

ServerIron ADX(config-rs-R4)# port http

ServerIron ADX(config-rs-R4)# exit

Primary Servers

ServerIron ADX(config-rs-R5)# server virtual-name VIP1 198.10.10.100

ServerIron ADX(config-vs-VIP1)# port http lb-pri-servers

ServerIron ADX(config-vs-VIP1)# bind http R2 http R3 http R4 http R5 http

Backup Servers

VIP

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Clone Real Server Configuration

Auto binding of cloned server to VIP

ServerIron ADX(config)# server real RS1 1.2.3.4

ServerIron ADX(config-rs-rs1)# clone-server RS2 5.6.7.8

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Session Persistence: Sticky vs. Concurrent

End of Module 5: Server Load Balancing

Revision 0310