Chapter 4: Managing Virtual Servers

Virtual servers represent groups of real servers and are associated with real server farms through policies. CVDM-CSM displays the details of the configured virtual servers and allows you to create or delete virtual servers, associate them with server farms and policies, enable specific client IP addresses to connect to the virtual servers, and turn the virtual services on or off.

To configure a virtual server, you set its attributes by specifying the default server farm (default policy) and associate other server farms through a list of policies. The default policy is used if a request does not match any SLB policies or if there are no policies associated with the virtual server. Before you associate a server farm with the virtual server, you must configure the server farm.

Server farms that function as virtual servers can improve scalability and availability of services for your network. You can add new servers or remove failed servers at any time without affecting the virtual server's availability. A server farm must be configured before associating it to the virtual server.

Instead of using a virtual server on the CVDM-CSM for the server-side connection, you can now configure it to forward packets directly to a real server. To do this, the CVDM-CSM must have the virtual server configured for predictor-forward. Additionally, for all real servers for which direct forwarding of connections is to be done, each real server must be assigned to a server farm that is not associated with any virtual server.

To enable partial server farm failover, you can now define the threshold number of real servers to be out of service for the backup server farm to take over. You can also define the number of real servers to be in service for the server farm to be considered active.

Viewing Virtual Servers

•

Click Home at the top of the window and click Virtual Servers under Services Dashboard.

•

Click Setup from the task bar and click Virtual Servers in the Setup pane.


Columns	Description
Name	Name of the virtual server.
Virtual IP Address	IP address of the virtual server.
VLAN ID	Specify a VLAN for incoming traffic from the list. •If it is All, traffic from all VLANs is enabled. •If it is Local, CSM-S directly forwards the packets to the real server.
Protocol	Specifies the load-balancing protocol used for virtual server traffic. You can choose from the following, or enter a number from 1 to 255. •TCP •UDP •ANY
Port	TCP/UDP port number used by the protocol.
Server Farm	Name of the default server farm associated to the real server.
Backup Farm	Name of the backup server farm associated to the real server.
Admin Status	Lets you know the administrative status of the virtual server.
Operational Status	Lets you know the operational status of the virtual server.

To group the virtual servers, click

on top of the object selector; then select one of the following options from the list:

•

Click Set Admin Status to instantly set the status of the virtual server.

Adding a Virtual Server

•

Click Home at the top of the window and click Virtual Servers under Services Dashboard.

•

Click Setup from the task bar and click Virtual Servers in the Setup pane.

Step 3

Click one of the following tabs, then proceed to the corresponding section in this guide for configuration information:

General


Columns	Action/Description
Name	Enter the name of the virtual server.
Status	From the list, select the status of the virtual server.
VLAN ID	From the list, specify a VLAN for incoming traffic. •If you choose All, traffic from all VLANs is enabled. •If you choose Local, CSM-S directly forwards the packets to the real server.
Virtual IP Address
IP Address	Enter the IP Address of the virtual server.
Protocol	From the list, select the load-balancing protocol for virtual server traffic. You can choose from Any, TCP, or UDP, or enter a number from 1 to 255. This field is enabled only when you enter the IP address.
Port	From the list, select the port number. This field is enabled only when you choose TCP or UDP.
Service Type	From the list, select the service type. You can combine connections associated with the same service. This allows all related connections from a client to use a particular real server. The options depend on the protocol you choose. You can choose from the following: •FTP—Combines connections to FTP port 21. •RTSP—Combines connections to Real Time Streaming Protocol (RTSP) TCP port 554. •Termination—Enables TCP termination for DoS attack protection. •Per-packet—Load balances each packet independently. This option is for non-TCP only.
Mask	Specify the virtual IP mask.
Advertise
Advertise Virtual IP	Select this to advertise the IP address of the virtual server as the host route.
Advertise only if reals are active	Select this to advertise only if real servers are active.

Policies

•

Click Add and select one of the following to associate policies to the virtual server:

–

Create Policy—Allows you to create a policy. For more information, see Adding Policies, page 7-5.

•

Select a policy from the table and click Delete to remove policies from the virtual server.

Note Be sure to put the policies in the right order. Traffic is routed based on the order of the policies.

Default Policy

Click the Default Policy tab to configure a virtual server to operate at Level 4. You can specify the server farm (default policy) and backup server farms. You can configure a backup server farm to operate when a server farm is out of service.


Column	Action/Description
Default Server Farm	Click and select one of the following: •Select Server Farm—Allows you to select one from a list of server farms. •Create Server Farm—Allows you to create a server farm. For more information, see Adding Server Farms, page 5-5. •Clear Server Farm—Allows you to clear the field.
Backup Server Farm
Server Farm	Click and select one of the following: •Select Server Farm—Allows you to select a server farm from a list. •Create Server Farm—Allows you to create a server farm. For more information, see Adding Server Farms, page 5-5. •Clear Server Farm—Allows you to clear the field.
Sticky	Select this check box to enable the sticky property. This ensures that multiple connections from the same client, that match the same SLB policy stick (or attach) to the same real server.
Threshold
Reals Inservice	The number of real servers to be in service for the server farm to be active.
Reals Out of Service	The number of real servers to be out of service for the backup server farm to take over.

Client Restriction

Click the Client Restriction tab to add details of the clients restricted to use the virtual server.

•

Select a row in the table and click Delete to delete the selected client.

Sticky Connections

Sticky connections are connections from a client that conform to an SLB policy. Sticky connections use the same real server for subsequent connections. To ensure that the CVDM-CSM changes its connections to the opposite direction and sends them back to the source, you can configure a reverse sticky group.


Column	Description
Sticky Timer	Specifies the period of time (in minutes) that the sticky information is kept.
Mask	From the list, select, Class A, Class B, Class A, and Class D masks. If it is not specified, the default for network mask is 255.255.255.255.
Sticky Group	Click and select one of the following: •Select Sticky Group—Allows you to select a sticky group from a list. •Create Sticky Group—Allows you to create a sticky group. For more information, see Adding a Sticky Group, page 9-6. •Clear Sticky Group—Allows you to clear the field.
Reverse Sticky Group	Click and select one of the following: •Select Sticky Group—Allows you to select from a list of sticky groups. •Create Sticky Group—Allows you to create a sticky group. For more information, see Adding a Sticky Group, page 9-6. •Clear Sticky Group—Allows you to clear the field.
SSL Sticky	You can stick an incoming SSL connection based only on the offset and length values of the SSL ID.
Offset	Enter the offset for the SSL ID.
Length	Enter the length of the SSL ID.

Other

Click the Other tab to configure performance, load, and traffic parameters. You can configure each virtual server with a pending connection timeout to terminate connections quickly if the switch becomes flooded with traffic.


Column	Description
Performance/Load Parameters
Idle Timer	Enter the idle connection timer duration (in seconds). This is the time (in seconds) that connection information is maintained, in the absence of packet activity, for a connection
Pending Timeout	Enter the time (in seconds) to wait before a connection is considered unreachable.
Parse Length	Enter the maximum number of bytes to parse for URLs and cookies.
Maximum Connections	Enter the maximum number of active connections on the real server.
URL Hash	Select this check box to enable URL hash load-balancing algorithm. You can enable the Begin Pattern and End Pattern fields only if you select this check box. For more information on URL Hashing, see Configuring URL Hashing.
Begin Pattern	Specify the beginning pattern of the URL to parse.
End Pattern	Specify the ending pattern of the URL to parse.
Connection/Traffic Parameters
Enable HTTP Persistence	Select this to enable or disable HTTP persistence for connections on the virtual server.
Enable Unidirectional Traffic	Select this to enable unidirectional traffic.

Configuring URL Hashing

When you choose a server farm for a connection, you can select a specific real server in that server farm. You can choose least connections, round robin, or URL hashing to select a real server.

URL hashing is a load-balancing predictor for Layer 7 connections. You can configure URL hashing on CVDM-CSM on a server farm-by-server farm basis. CVDM-CSM chooses the real server by using a hash value based on a URL. This hash value may be computed on the entire URL or on a portion of it.

You can specify the beginning and ending patterns in the URL to select only a portion of the URL for hashing. Hashing occurs from the start of the specified beginning pattern through the specified ending pattern.

For example, in the following URL, if the beginning pattern is c&k=, and the ending pattern is &, only the substring c&k=c is hashed:

Note

Beginning and ending patterns are restricted to fixed constant strings. You cannot specify general regular expressions as patterns. If you do not specify the beginning pattern, hashing begins at the beginning of the URL. If you do not specify the ending patter, hashing ends at the end of the URL.

Editing a Virtual Server

You can edit virtual server connection details and the list of policies for the selected virtual servers.

•

Click Home at the top of the window and click Virtual Servers under Services Dashboard.

•

Click Setup from the task bar and click Virtual Servers in the Setup pane.

Step 2

Select a row from the table. Click Edit. The Edit Virtual Server dialog box appears.

Step 3

Click one of the following tabs, then proceed to the corresponding section for configuration information:

General


Column	Action/Description
Name	The name of the virtual server.
Status	From the list, select the status of the virtual server.
VLAN ID	From the list, specify a VLAN for incoming traffic. •If you choose All, traffic from all VLANs is enabled. •If you choose Local, CSM-S directly forwards the packets to the real server.
Virtual IP Address
IP Address	Enter the IP address of the virtual server.
Protocol	From the list, select the load-balancing protocol for virtual server traffic. You can choose from Any, TCP, or UDP, or enter a number from 1 to 255.
Port	From the list, select the port number. This field is enabled only when you choose TCP or UDP.
Service Type	From the list, select the service type. You can combine connections associated with the same service. This allows all related connections from a client to use a particular real server. The options depend on the protocol you choose. You can choose from the following: •FTP—Combines connections to FTP port 21. •RTSP—Combines connections to the Real Time Streaming Protocol (RTSP) TCP port 554. •Termination—Enables TCP termination for DoS attack protection. •Per-packet—Load balances each packet independently. This option is for non-TCP only.
Advertise
Advertise Virtual IP	Select this to advertise the IP address of the virtual server as the host route.
Advertise only if reals are active	Select this to advertise only if real servers are active.

Policies

•

Click Add to associate policies to the virtual server. For more information, see Adding Policies, page 7-5.

Note Be sure to put the policies in the right order. Traffic is routed based on the order of the policies.

Default Policy


Column	Action/Description
Default Server Farm	Click and select one of the following: •Select Server Farm—Allows you to select a server farms from a list. •Create Server Farm—Allows you to create a server farm. For more information, see Adding Server Farms, page 5-5. •Clear Server Farm—Allows you to clear the field.
Backup Server Farm
Server Farm	Click and select one of the following: •Select Server Farm—Allows you to select a server farms from a list. •Create Server Farm—Allows you to create a server farm. For more information, see Adding Server Farms, page 5-5. •Clear Server Farm—Allows you to clear the field.
Sticky	Select this check box to enable the sticky property. This ensures that multiple connections from the same client that match the same SLB policy stick (or attach) to the same real server.
Threshold
Reals Inservice	The number of real servers to be in service for the server farm to be active.
Reals out of service	The number of real servers to be out of service for the backup server farm to take over.

Client Restriction

Click the Client Restriction tab to add details of the clients restricted to use the virtual server. You have the following options:

•

Select a row in the table and click Delete to delete the selected client restriction.

Sticky Connections

Field	Description
IP Address	IP Address of the client.
Mask	Specify the type of IP mask. It can be from Class A, Class B, Class C, or Class D masks. If it is not specified, the default for network mask is 255.255.255.255.
Exclude this Client	Select this check box to exclude traffic from this client.


Column	Description
Sticky Timer	Specifies the period of time (in minutes) that the sticky information is kept.
Mask	From the list, select, Class A, Class B, Class A and Class D masks. If it is not specified, the default for network mask is 255.255.255.255.
Sticky Group	Click and select one of the following: •Select Sticky Group—Allows you to select a sticky group from a list. •Create Sticky Group—Allows you to create a sticky group. For more information, see Adding a Sticky Group, page 9-6. •Clear Sticky Group—Allows you to clear the field.
Reverse Sticky Group	Click and select one of the following: •Select Sticky Group—Allows you to select a sticky group from a list. •Create Sticky Group—Allows you to create a sticky group. For more information, see Adding a Sticky Group, page 9-6. •Clear Sticky Group—Allows you to clear the field.
SSL Sticky	You can stick an incoming SSL connection based only on the offset and length values of the SSL ID.
Offset	Enter the offset for the SSL ID.
Length	Enter the length of the SSL ID.

Other

Click the Other tab to edit details of performance, load, and traffic parameters. You can configure each virtual server with a pending connection timeout to terminate connections quickly if the switch becomes flooded with traffic.


Column	Description
Performance/Load Parameters
Idle Timer	Enter the idle connection timer duration (in seconds). This is the time that connection information is maintained, in the absence of packet activity, for a connection
Pending Timeout	Enter the time (in seconds) to wait before a connection is considered unreachable.
Parse Length	Enter the maximum number of bytes to parse for URLs and cookies.
Maximum Connections	Enter the maximum number of active connections on the real server.
URL Hash	Select this check box to enable URL hash load-balancing algorithm. You can enable the Begin Pattern and End Pattern fields only if you select this check box. For more information on URL Hashing, see Configuring URL Hashing.
Begin Pattern	Specify the beginning pattern of the URL to parse.
End Pattern	Specify the ending pattern of the URL to parse.
Connection/Traffic Parameters
Enable HTTP Persistence	Select this to enable or disable HTTP persistence for connections on the virtual server.
Enable Unidirectional Traffic	Select this to enable unidirectional traffic.

Viewing an Individual Virtual Server

You can view the configuration details of each virtual server when you click any of them. When a virtual server is out of service it turns red, and when it is in service it turns green.

•

Click Home at the top of the window and click Virtual Servers under Services Dashboard.

•

Click Setup from the task bar and click Virtual Servers in the Setup pane.

Step 2

Click a virtual server to view its configuration details. The virtual server table appears, displaying the following columns.


Column	Description
Admin Status	Lets you know the administrative status of the real server.
Operational Status	Lets you know the operational status of the virtual server.
Virtual IP Address	IP address of the virtual server.
Protocol	From the list, select the load-balancing protocol for virtual server traffic. You can choose from Any, TCP, or UDP, or enter a number from 1 to 255.
Mask	Type of IP mask. It can be a Class A, Class B, Class C, or Class D mask. If it is not specified, the default for network mask is 255.255.255.255.
Port	Port alloted for the traffic. This field is enabled only when you choose TCP or UDP.
VLAN ID	Specifies the VLAN for incoming traffic. •If it is All, traffic from all VLANs is enabled. •If it is Local, CSM-S directly forwards the packets to the real server.
Service Type	Specifies the service type. You can combine connections associated with the same service. This allows all related connections from a client to use a particular real server. The options depend on the protocol you choose. You can choose from the following: •FTP—Combines connections to FTP port 21. •RTSP—Combines connections to the Real Time Streaming Protocol (RTSP) TCP port 554. •Termination—Enables TCP termination for DoS attack protection. •Per-packet—Load balances each packet independently. This option is for non-TCP only.
Advertise
Advertise Virtual IP	Select this to advertise the IP address of the virtual server as the host route.
Advertise only if reals are active	Select this to advertise only if real servers are active.
Enable HTTP Persistence	Select this to enable or disable HTTP persistence for connections in the virtual server.
Enable Unidirectional Traffic	Select this to enable unidirectional traffic.

Step 3

Click one of the following tabs, then proceed to the corresponding section for configuration information:

Policies


Field	Description
Policy Name	Policy associated with a virtual server.
Conditions
Cookie Map	Name of the cookie map associated with a policy. Only one cookie map can be associated with a policy.
URL Map	Name of the URL map associated with a policy. Only one URL map can be associated with a policy.
Header Map	Name of the Header map associated with a policy. Only one Header map can be associated with a policy.
Client Group	Client group can be either standard access lists names or an ID from 1 to 99. Only one client group can be associated with a given SLB policy.
Action
•Server Farm •Backup Server Farm	Name of the server farm associated to the real server. You can choose one server farm and/or backup server farm to associate to the policy.
•Server Farm •Backup Server Farm
Sticky Group	Number identifying the sticky group to which the virtual server belongs.
Reverse Sticky Group	Number identifying the reverse sticky group to which the virtual server belongs.

Default Policy


Column	Action/Description
Server Farm
Associated Real Servers
Real	Real server associated to the Server farms through policies.
Local SSL	Indicates if the real server is the SSL card.
Minimum Connections	Minimum number of connections to the real server.
Maximum Connections	Maximum number of connections to the real server.
Weight	Weight assigned to the real server. The weight identifies the capacity of the real server compared to other real servers in the server farm.
Admin Status	Lets you know the status of the real server.

Backup Server Farm

Click the Backup Server Farm tab to view the details of the backup server farm.


Column	Action/Description
Backup Server Farm
Sticky	Select this check box to enable the sticky property. This ensures that multiple connections from the same client that conform to an SLB policy stick (or attach) to the same real server.
Associated Real Servers
Real	Real server associated to the Server farms through policies.
Local SSL	Indicates if the real server is the SSL card.
Minimum Connections	Minimum number of active connections on the real server.
Maximum Connections	Maximum number of active connections on the real server.
Weight	Weight assigned to the real server. The weight identifies the capacity of the real server compared to other real servers in the server farm.
Admin Status	Lets you know the status of the real server.

Client and Sticky Connections

Click the Client/Sticky Connections tab to view details of the restricted clients and sticky connections. The following information appears:


Column	Description
Client Restriction
IP Address	IP address of the client to be restricted.
Mask	Specify the type of IP mask. It can be from Class A, Class B, Class C or Class D masks. If it is not specified, the default for network mask is 255.255.255.255.
Exclude	If this check box is selected, traffic from this client will be excluded.
Sticky Connections
Sticky Timer	Specifies the period of time (in minutes) that the sticky information is kept.
Mask	Specifies if it is a Class A, Class B, Class A and Class D mask. If it is not specified, the default for network mask is 255.255.255.255.
Sticky Group	Sticky group associated with the virtual server.
Reverse Sticky	Number identifying the reverse sticky group to which the virtual server belongs.
SSL Sticky	You can stick an incoming SSL connection based only on the offset and length values of the SSL ID.
Offset	The offset for the SSL ID.
Length	The length of the SSL ID.

Other Parameters

Click the Other Parameters tab to view details of performance, load and traffic related parameters. You can configure each virtual server with a pending connection timeout to terminate connections quickly if the switch becomes flooded with traffic.

You can limit the number of connections going through the CVDM-CSM to a particular virtual server by specifying the maximum and minimum number of connections.


Field	Description
Performance/Load Parameters
Idle Timer	Enter the idle connection timer duration (in seconds). This is the time that connection information is maintained, in the absence of packet activity, for a connection
Pending Timeout	Enter the time (in seconds) to wait before a connection is considered unreachable.
Parse Length	Enter the maximum number of bytes to parse for URLs and cookies.
Maximum Connections	Enter the maximum number of connections to the real server.
URL Hash	Select this check box to enable URL hash load-balancing algorithm. You can enable the Begin Pattern and End Pattern fields only if you select this check box. For more information on URL Hashing, see Configuring URL Hashing.
Begin Pattern	Specify the beginning pattern of the URL to parse.
End Pattern	Specify the ending pattern of the URL to parse.
Connection/Traffic Parameters
Enable HTTP Persistence	Select this check box to enable or disable HTTP persistence for connections in the virtual server.
Enable Unidirectional Traffic	Select this check box to enable unidirectional traffic.

Viewing a Policy

You can view the details of the conditions and actions of the policy associated with each virtual server.

•

Click Home at the top of the window and click Virtual Servers under Services Dashboard.

•

Click Setup from the task bar and click Virtual Servers in the Setup pane.

Step 2

Select the required virtual server and click the policy associated with it.

Viewing a Default Policy

You can view the details of the default policy associated with each virtual server.

•

Click Home at the top of the window and click Virtual Servers under Services Dashboard.

•

Click Setup from the task bar and click Virtual Servers in the Setup pane.

Step 2

Select a virtual server and click the default policy associated with it.

Step 3

Click one of the following tabs, then proceed to the corresponding section for configuration information:

Server Farms

Click the Server Farms tab to view details of all the server farms that are associated to a policy.


Field	Description
Server Farm	You can create or choose one server farm to associate it to the policy. Click and select one of the following: •Select Server Farm—Allows you to select a server farm from the list. •Create Server Farm—Allows you to create a server farm. For more information, see Adding Server Farms, page 5-5.
Associated Real Servers
Real	Real server associated to the Server farms through the policy.
Local SSL	Indicates if the real server is the SSL card.
Minimum Connections	Minimum number of connections to the real server.
Maximum Connections	Maximum number of connections to the real server.
Weight	Weight assigned to the real server. The weight identifies the capacity of the real server compared to other real servers in the server farm.
Admin Status	Lets you know the status of the real server.

Backup Server Farms

Click the Backup Server Farms tab to view details of all the backup server farms that are associated to this policy.


Column	Description
Backup Server Farm	You can create or choose one backup server farm to associate it to the policy. Click and select one of the following: •Select Server Farm—Allows you to select a backup server farm from the list. •Create Server Farm—Allows you to create a backup server farm. For more information, see Adding Server Farms, page 5-5.
Sticky	Select this check box to enable the sticky property. This ensures that multiple connections from the same client that match the same SLB policy stick (or attach) to the same real server.
Associated Real Servers
Real	Real server associated to the Server farms through the policy.
Local SSL	Indicates if the real server is the SSL card.
Minimum Connections	Minimum number of connections to the real server.
Maximum Connections	Maximum number of connections to the real server.
Weight	Weight assigned to the real server. The weight identifies the capacity of the real server compared to other real servers in the server farm.
Admin Status	Lets you know the status of the real server.

Client Restrictions

Sticky Connections

Field	Description
IP Address	IP Address of the client.
Mask	Specify the type of IP mask. It can be from Class A, Class B, Class C, or Class D masks. If it is not specified, the default for network mask is 255.255.255.255.
Exclude	Select this check box to exclude traffic from this client.


Field	Description
Sticky Timer	Specifies the duration of time (in minutes) that the sticky information is kept.
Mask	From the list, select Class A, Class B, Class A, and Class D masks. If it is not specified, the default for network mask is 255.255.255.255.
Sticky Group	Specify the sticky group associated with the virtual server.
Reverse Sticky Group	Enter the number identifying the reverse sticky group to which the virtual server belongs.
SSL Sticky	You can stick an incoming SSL connection based only on the offset and length values of the SSL ID.
Offset	Enter the offset for the SSL ID.
Length	Enter the length of the SSL ID.

Table Of Contents

Managing Virtual Servers

Viewing Virtual Servers

Adding a Virtual Server

General

Policies

Default Policy

Client Restriction

Sticky Connections

Other

Configuring URL Hashing

Editing a Virtual Server

General

Policies

Default Policy

Client Restriction

Sticky Connections

Other

Viewing an Individual Virtual Server

Policies

Default Policy

Backup Server Farm

Client and Sticky Connections

Other Parameters

Viewing a Policy

Viewing a Default Policy

Server Farms

Backup Server Farms

Client Restrictions

Sticky Connections