Advanced SLB High Availability and Stateless SLB...VRRP and VIP Groups are used to control the...

Advanced SLB High Availability and Stateless SLB

© 2009 Brocade Communications Systems, Inc.

All Rights Reserved. 2

Objectives

Upon completion of this module, you will be able to:

– Describe Server Load Balancing (SLB) high availability

– Distinguish between different high availability options

– Describe Sym-Active SLB configuration

– Describe stateless and stateful SLB

– Perform the lab exercises



High Availability Options on the ADX

Hot Standby SLB:

– One Brocade ServerIron ADX (ADX) is always active while the other

ADX is always standby.

Symmetric SLB (active-standby):

– Both ADXs can receive SLB traffic, but only the active VIP handles the

L4-7 SLB traffic, while the standby VIP functions as a standby.

Sym-Active SLB (active-active):

– Both ADXs can receive SLB traffic, and both are active for the same

VIP. Configuring sym-active and sym-priority on the VIP enables a

device to process traffic in active-active mode.



Hot Standby SLB

One ADX is active while other constantly checks the active ADX



Symmetric SLB

VIPs active on one ADX are backup on the other ADX; this is

based on the sym-priority parameter



Sym-Active SLB (Active-Active)

The same VIPs are active on both ADXs



High Availability — Dual L2 Switches

More resiliency in case of a failure



High Availability

Full redundancy at all levels



High Availability — Redundant DSR



High Availability

Active-standby server network interfaces



High Availability (cont.)

Sym-Active SLB ADXs with active-active dual-homed servers



Hot Standby Redundancy — Boot Up Sequence

On boot, the ADX checks for a private link (sync-link), if not present

the ADX becomes the active ADX

If a private link is present, the ADX listens for the presence of a

primary ADX

If the ADX detects a primary (active ADX) through its backup

monitoring port, the ADX is placed in standby mode

If the ADX does not detect a primary within one second then the

ADX becomes the primary ADX



Hot Standby Failover Algorithm

1. Does the active ADX have more healthy router ports than the standby

ADX?

– Yes: The active ADX remains active

– No: Go to Step 2

2. Do the active and standby ADXs have the same number of healthy

router ports?

– Yes: Go to Step 3

– No: SLB fails-over to the standby ADX since it has more healthy router

ports

3. Does the active ADX have the same number or more of healthy server

ports than the standby ADX?

– Yes: The active ADX remains active

– No: SLB fails-over to the standby ADX since it has more healthy server

ports, even though both ADXs have the same number of healthy router

ports



Sym-Active SLB



Configuring Symmetric SLB Priority

This command assigns a high priority of 254 to VIP1 for load

balancing on this ADX

Syntax: [no] sym-priority <num>

Example:

ADX(config)# server virtual-name VIP1 1.2.3.4

ADX(config-vs-VIP1)# sym-priority 254



Displaying Symmetric SLB Information

Use the show server symmetric command to display

Symmetric SLB information

Syntax: show server symmetric

Example:

ADX(config)# show server symmetric

Server Symmetric port = 1

Group_id = 1 Candidate cnt = 0

Port No-rx

1 100824



Configuring Sym-Active SLB

The sym-active command makes the high availability config into

an active-active config

Syntax: [no] sym-active

Example:

ADX(config)# server virtual-name VIP1 1.1.1.1

ADX(config-vs-VIP1)# port 80

ADX(config-vs-VIP1)# sym-priority 69

ADX(config-vs-VIP1)# sym-active



Enable Session Synchronization on an Application

This allows session synchronization to happen for port 80 (HTTP)

Syntax: server port <TCP/UDP-portnum>

Syntax: [no] session-sync

Example:

ADX(config)# server port 80

ADX(config-port-80)# session-sync



Configure a VIP Group

The VIP Group defines a collection of VIPs that fail over together to

the backup if the active fails

Syntax: [no] server vip-group <number>

Example:

ADX(config)# server vip-group 1

ADX(config-vip-group-[1])# vip 10.10.1.100

ADX(config-vip-group-[1])# exit



Bind VIP Group to a VRID

This allows a VIP Group to be associated to a Virtual Router ID

(VRID)

Syntax:[no] ip vrrp vrid 1

Syntax:[no] vip-group 1

Example:

ADX(config)# router vrrp (-extended)

ADX(config)# interface e1/2

ADX(config-if-e100-1/2)# ip vrrp vrid 1

ADX(config-if-e100-12-vrid-1)# vip-group 1



Sym-Active SLB Using VRRP-E

Must have Layer 2 connection between two ADXs

Must exchange Layer 3 broadcast

Must be in same subnet as VIPs

Same VIP must balance all requests for a given VIP

Must share the session table information



Dynamic Symmetric SLB Priority

Symmetric SLB (SSLB) can automatically adjust a VIP application’s

SSLB priority to a lower value if a given application fails a health

check

By default, the priority determines which ADX becomes the active

one for the VIP and application

Starts off with a predefined priority

When VIP application fails, Symmetric SLB priority is decremented

All VIP bound applications must fail for priority to decrement

Priority of 0 (zero) turns off Symmetric SLB



Configure Dynamic Sym Priority Factor

This allows the priority to be decremented by the value of the factor

for VIP failure

Syntax: [no] dyn-sym-pri-factor <num>

– The <num> parameter can be a value from 1 – 255 and specifies the

amount by which you want the ADX to decrement a VIPs priority when

an application on the VIP fails a health check

Example:

ADX_B(config-vs-VIP1)# sym-priority 30

ADX_B(config-vs-VIP1)# dyn-sym-pri-factor 9



The show server virtual Command

This command shows the status, VIP, and ports on the virtual side;

Enabled is a good state

Server Name: VIP1 IP : 2.3.4.5 : 1

Status: enabled Predictor: least-conn TotConn: 0

Dynamic: No HTTP redirect: disabled

Intercept: No

ACL: id = 0

Sym: group = 1 state = 5 priority = 30 keep = 0

dyn priority/factor = 21/ 9

Activates = 1, Inactive= 0

Best-standby-mac = 0000.0000.0000

Port State Sticky Concur Proxy CurConn TotConn PeakConn

ftp enabled NO NO NO 0 0

http enabled NO NO NO 0 0 0

default enabled NO NO NO 0 0 0



Configuring Failover Based on Active VIP Count

This allows you to configure ADX to failover based on number of

active VIPs and not router ports

Syntax: [no] server backup-vip-count

Example: ADX(config)# server backup-vip-cnt



Configuring Failover Based on the Number of

Active Virtual Ports

Allows failover to happen based on number of active virtual ports

Syntax: [no] server backup-vport-count

Example:

ADX(config)# server backup-vport-cnt



Configuring Delayed Failover

This allows the failover to be delayed for a specified time before

going into effect

Syntax: [no] server backup-delay-seconds <backup-

wait-seconds>

Example:

ADX(config)# server backup-delay-seconds 20

Active-Active in Routing Mode

Lab 11



Active-Active in Routing Mode Lab Exercise

Stateless Server Load Balancing



Stateful and Stateless Server Load Balancing

Stateful load balancing:

– Uses session table entries to track connections between the client and

server, and requires the server responses to pass back through the

ADX

Stateless load balancing:

– Does not create session table entries and does not require the server

response to pass back through the ADX

– Typically used by applications that are not context sensitive



Stateless Server Load Balancing

Stateless port

No session in session table

Hash algorithm to select real server

– Uses request’s source IP/UDP port and IP address

Can be disabled for UDP

– Uses Round Robin



Disabling Hashing for UDP DNS Traffic

Turn off hashing for stateless DNS traffic

Syntax: [no] port <udp-portnum> stateless no-hash

Example:

ADX(config)# server virtual VIP1 192.168.4.69

ADX(config-vs-VIP1)# port dns stateless no-hash



Stateless Server Load Balancing for HTTP Traffic

Makes HTTP traffic stateless under the VIP configuration

Syntax: [no] port http stateless

Example:

ADX(config)# server virtual StatelessHTTP 192.168.4.69

ADX(config-vs-StatelessHTTP)# port http stateless

ADX(config-vs-StatelessHTTP)# bind http R1 http

ADX(config-vs-StatelessHTTP)# bind http R2 http



Summary

ADX provides robust HA solutions

The three main HA options are, Hot standby, active standby and

Sym-Active (also called active-active)

Sym-priority and Sym-Active are two configuration parameters that

control the sym active HA mode

ADX supports both stateful and stateless applications. By default,

applications are stateful

VRRP and VIP Groups are used to control the operation of the HA

modes

Advanced SLB High Availability and Stateless SLB

Date post:	17-Mar-2021
Category:	Documents
Upload:	others
View:	8 times
Download:	0 times

Advanced SLB High Availability and Stateless SLB...VRRP and VIP Groups are used to control the...

Documents