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Configure GSLB service selection using content switching

September 14, 2021
Contributed by: 
S C

In a typical GSLB deployment, you can prioritize the selection of a set of GSLB services bound to a GSLB virtual server, but you cannot do the following:

  • Restrict the selection of a GSLB service from a subset of GSLB services bound to a GSLB virtual server for the given domain.
  • Apply different load balancing methods on the different subsets of GSLB services in the deployment.
  • Apply spillover policies on a subset of GSLB services, and you cannot have a backup for a subset of GSLB services.
  • Configure a subset of GSLB services to serve different content. That is, you cannot content switch between servers in different GSLB sites. The GSLB configuration assumes that the servers contain the same content.
  • Define a subset GSLB service with different priorities and specify an order in which the services in the subset are applied to a request.

You can now configure a content switching (CS) policy to customize the GSLB deployment. First configure a set of GSLB services and bind it to a GSLB virtual server. Then, configure a CS virtual server of target type GSLB, define a CS policy and action with the GSLB virtual server as target virtual server, and bind the CS policy to CS virtual server.

Important

  • Only CS policies with DNS based expressions can be bound to a CS virtual server of target type GSLB.
  • If a GLSB service is bound to a CS virtual server through a GSLB virtual server, you cannot bind another GSLB virtual server bound with the same GSLB service to the CS virtual server.

Example Consider a GLSB deployment that includes two GSLB sites. At each site, four GSLB services (S-1, S-2, S-3, and S-4) are bound to GSLB virtual server VS-1. You can configure a content switching (CS) virtual server of target type GSLB and define a CS policy and action with VS-1 as the target virtual server, so that requests for content in English are served only by S-1 and S-2, and requests for content in the local language are served only by S-3 and S-4.

You can give S-1 priority by configuring a backup virtual server to VS-1 and binding S-2 to the backup virtual server. S-1 serves the client requests. If the server S-1 represents goes down, S-2 serves the requests. If both S-1 and S-2 are down, clients receive an empty response.

To configure GSLB Service Selection using Content Switching:

  1. Configure GSLB. For instructions, see Configuring Global Server Load Balancing.
  2. Configure a Content Switching (CS) virtual server of target type GSLB. For more information, see Creating Content Switching Virtual Servers.
  3. Configure Content Switching (CS) policies. For more information, see Configuring Content Switching Policies.
  4. Configure CS actions that designate a GSLB virtual server as the target virtual server. For more information, see Configuring a Content Switching Action.
  5. Bind the CS policies to the CS virtual server. For more information, see Binding Policies to a Content Switching Virtual Server.
  6. Bind the domain to the CS virtual server instead of the GSLB virtual server.

Sample Configuration

The following sample configuration sends requests from the client with IP address 5.5.5.5 to SERVICE_GSLB1 and SERVICE_GSLB2. SERVICE_GSLB1 has a higher priority than SERVICE_GSLB2, and SERVICE_GSLB2 serves the client requests only when SERVICE_GSLB1 is down. If both SERVICE_GSLB1 and SERVICE_GSLB2 are down, SERVICE_GSLB3 and service-GSLB4 are not considered, and a blank response is sent to the client.

add cs vs CSVSERVER_GSLB http –targettype GSLB
Done
add gslb vs VSERVER_GSLB1 http
Done
add gslb vs VSERVER_GSLB2 http
Done
add gslb vs VSERVER_GSLB_BACKUP1 http
Done
set gslb vs VSERVER_GSLB1 -backupvserver VSERVER_GSLB_BACKUP1
Done
add gslb service SERVICE_GSLB1 1.1.1.1 HTTP 80 -sitename site1
Done
add gslb service SERVICE_GSLB2 1.1.1.2 HTTP 80 -sitename site1
Done
add gslb service SERVICE_GSLB3 1.1.1.3 HTTP 80 -sitename site2
Done
add gslb service SERVICE_GSLB4 1.1.1.4 HTTP 80 -sitename site2
Done
bind gslb vs VSERVER_GSLB1 -servicename SERVICE_GSLB1
Done
bind gslb vs VSERVER_GSLB_BACKUP1 -servicename SERVICE_GSLB2
Done
bind gslb vs VSERVER_GSLB2 -servicename SERVICE_GSLB3
Done
bind gslb vs VSERVER_GSLB2 -servicename SERVICE_GSLB4
Done
add cs action a1 -targetvserver VSERVER_GSLB1
Done
add cs policy p1 -rule "CLIENT.IP.SRC.EQ(5.5.5.5)" -action a1
Done
bind cs vs CSVSERVER_GSLB -domainName www.abc.com
Done
bind cs vs CSVSERVER_GSLB -policyname p1 -priority 1
Done
add cs action a2 -targetvserver VSERVER_GSLB2
Done
add cs policy p2 -rule "CLIENT.IP.SRC.EQ(6.6.6.6)" -action a2
Done
bind cs vs CSVSERVER_GSLB -policyname p2 -priority 2
Done
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Associate a target virtual server expression to a GSLB content switching action

You can now associate a target virtual server expression to a GSLB content switching action. This allows GSLB content switching virtual server to use policy expressions to compose the target GSLB virtual server name while processing the DNS requests.

To configure a content switching action that specifies an expression by using the CLI

At the command prompt, type the following command to configure the content switching action to retrieve the HTTP callout response.

add cs action <name> -targetVserverExpr <expression>
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Example:

add cs action csact_GSLB_VServer -targetVserverExpr "SYS.HTTP_CALLOUT(GSLB_Method_API)"
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To configure a content switching action that specifies an expression by using the GUI

  1. Navigate to Traffic Management > Content Switching > Actions.
  2. Configure a content switching action, and specify an Expression that dynamically computes the name of the target load balancing virtual server.
Configure GSLB service selection using content switching
September 14, 2021
Contributed by: 
S C
September 14, 2021
Contributed by: 
S C

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