Catalyst 6500 Series Switch Content Switching Module with SSL (CSM-S) Installation and Configuration Note - Configuring Additional Features and Options [Cisco Services Modules]

Table Of Contents

Configuring Additional Features and Options

Configuring Session Persistence (Stickiness)

Configuring Sticky Groups

Cookie Insert

Cookie Sticky Offset and Length

URL-Learn

Configuring Route Health Injection

Understanding RHI

RHI Overview

Routing to VIP Addresses Without RHI

Routing to VIP Addresses With RHI

Understanding How the CSM-S Determines VIP Availability

Understanding Propagation of VIP Availability Information

Configuring RHI for Virtual Servers

Environmental Variables

Configuring Persistent Connections

HTTP Header Insert

Configuring Global Server Load Balancing

Using the GSLB Advanced Feature Set Option

Configuring GSLB

Configuring Network Management

Configuring SNMP Traps for Real Servers

Configuring the XML Interface

Configuring Server Application State Protocol

Configuring SASP Groups

Configuring a GWM

Configuring Alternate bind_ids

Configuring a Unique ID for the CSM-S

Configuring Weight Scaling

Back-End Encryption

Configuring the Client Side

Configuring the Server Side

Configuring the CSM-S as the Back-End Server

Configuring the Real Server as the Back-End Server

Configuring Additional Features and Options

This chapter describes how to configure content switching and contains these sections:

•Configuring Session Persistence (Stickiness)

•Configuring Route Health Injection

•Environmental Variables

•Configuring Persistent Connections

•HTTP Header Insert

•Configuring Global Server Load Balancing

•Configuring Network Management

•Configuring Server Application State Protocol

•Back-End Encryption

Configuring Session Persistence (Stickiness)

Session persistence (or stickiness) refers to the functionality of sending multiple (simultaneous or subsequent) connections from the same client consistently to the same server. This is a typical requirement in certain load-balancing environments.

Complete application transactions (such as browsing a website, selecting various items for purchase, and then checking out) typically require multiple—sometimes hundreds or thousands—simultaneous or subsequent connections. Most of these transactions generate and require temporary critical information. This information is stored and modified on the specific server that is handling the transaction. For the entire duration of the transaction, which may take from minutes to hours, the client has to be consistently sent to the same server.

Multi-tier designs with a back-end shared database partially remove the problem, but a good stickiness solution improves the performance of the application by relying on the local server cache. Using the local server cache removes the requirement to connect to the database and get the transaction-specific information each time that a new server is selected.

Uniquely identifying a client across multiple connections is the most difficult part of the stickiness problem. Whatever might be the key information used to recognize and identify a client, the load-balancing device must store that information and associate it with the server that is currently processing the transaction.

Note The CSM-S can maintain a sticky database of 256.000 entries.

The CSM-S can uniquely identify the clients and perform stickiness with the following methods:

•Source IP address stickiness

The CSM-S can be configured to learn the entire source IP address (with a netmask of 32 bits) or just a portion of it.

•SSL identification stickiness

When the client and servers are communicating over SSL, they maintain a unique SSL identification number across multiple connections. SSL version 3.0 or TLS 1.0 specify that this identification number must be carried in clear text. The CSM-S can use this value to identify a specific transaction, but because this SSL ID can be renegotiated, it is not always possible to preserve stickiness to the correct server. SSL ID-based stickiness is used to improve performance of SSL termination devices by consistently allowing SSL ID reuse.

Note When the CSM-S is used with the Catalyst 6500 SSL Module, SSL ID stickiness across SSL ID renegotiation is possible because each Catalyst 6500 SSL Module inserts its MAC address within the SSL ID, at a specific offset. This is configured through the ssl-sticky command under the virtual server configuration submode.

Refer to the Catalyst 6500 Series Switch SSL Services Module Configuration Note, Chapter 5 "Configuring Different Modes of Operation" for sticky connection configuration information.

Refer to the Catalyst 6500 Series Switch Content Switching Module Command Reference for information about the ssl-sticky command.

•Dynamic cookie learning

The CSM-S can be configured to look for a specific cookie name and automatically learn its value either from the client request HTTP header or from the server "set cookie" message.

By default, the entire cookie value is learned by the CSM-S. This feature has been enhanced in CSM-S software release 4.1.(1) by introducing an optional offset and length to instruct the CSM-S to only learn a portion of the cookie value. See the "Cookie Sticky Offset and Length" section.

Dynamic cookie learning is useful when dealing with applications that store more than just the session ID or user ID within the same cookie. Only specific bytes of the cookie value are relevant to stickiness.

CSM-S software release 4.1(1) also added the dynamic cookie stickiness feature that has the capability to search for (and eventually learn or stick to) the cookie information as part of the URL. (See the "URL-Learn" section.) URL learning is useful with applications that insert cookie information as part of the HTTP URL. In some cases, this feature can be used to work around clients that reject cookies.

•Cookie insert

The CSM-S inserts the cookie on behalf of the server, so that cookie stickiness can be performed even when the servers are not configured to set cookies. The cookie contains information that the CSM-S uses to ensure persistence to a specific real server.

Configuring Sticky Groups

Configuring a sticky group involves configuring the sticky method (source IP, SSL ID, cookie) and parameters of that group and associating it with a policy. The sticky timeout specifies the period of time that the sticky information is kept in the sticky tables. The default sticky timeout value is 1440 minutes (24 hours). The sticky timer for a specific entry is reset each time that a new connection matching that entry is opened.

The sticky timer for a specific entry is reset from the point where the last session ends. This timeout policy applies to sessions using IP_Sticky only. Sessions using other forms of persistence (for example, cookie and url-hash) are not affected by this behavior.

Use this command to configure the sticky environment variable:
Router(config-module-csm)# variable NO_TIMEOUT_IP_STICKY_ENTRIES 1
Note Multiple policies or virtual servers potentially can be configured with the same sticky group. In that case, the stickiness behavior applies to all connections to any of those policies or virtual servers. These connections are also referred to as "buddy connections" because a client stuck to server A through policy or virtual server 1 also will be stuck to the same server A through policy or virtual server 2, if both policy or virtual server 1 and 2 are configured with the same sticky group.

Caution When using the same sticky group under multiple policies or virtual servers, it is important to make sure that all are using the same server farm or a different server farm with the same servers in it.

To configure sticky groups, perform this task:
Command

Purpose
Router(config-module-csm)# sticky 
sticky-group-id {netmask netmask | cookie 
name | ssl} [address [source | destination | 
both]][timeout sticky-time] 
Ensures that connections from the same client matching the same policy use the same real server¹.
¹The no form of this command restores the defaults.
This example shows how to configure a sticky group and associate it with a policy:
Router(config-module-csm)# sticky 1 cookie foo timeout 100
Router(config-module-csm)# serverfarm pl_stick 
Router(config-slb-sfarm)# real 10.8.0.18 
Router(config-slb-real)# inservice
Router(config-slb-sfarm)# real 10.8.0.19
Router(config-slb-real)# inservice
Router(config-slb-real)# exit
Router(config-slb-sfarm)# exit
Router(config-module-csm)# policy policy_sticky_ck 
Router(config-slb-policy)# serverfarm pl_stick 
Router(config-slb-policy)# sticky-group 1
Router(config-slb-policy)# exit
Router(config-module-csm)# vserver vs_sticky_ck 
Router(config-slb-vserver)# virtual 10.8.0.125 tcp 90 
Router(config-slb-vserver)# slb-policy policy_sticky_ck
Router(config-slb-vserver)# inservice
Router(config-slb-vserver)# exit
Cookie Insert

Use cookie insert when you want to use a session cookie for persistence if the server is not currently setting the appropriate cookie. With this feature enabled, the CSM-S inserts the cookie in the response to the server from the client. The CSM-S then inserts a cookie in traffic flows from a server to the client.

This example shows how to specify a cookie for persistence:
Cat6k-2(config-module-csm)# sticky 5 cookie mycookie insert
Cookie Sticky Offset and Length

The cookie value may change with only a portion remaining constant throughout a transaction between the client and a server. The constant portion may be used to make persistent connections back to a specific server. To stick or maintain the persistence of that connection, you can specify the portion of the cookie that remains constant with the offset and length values of a cookie in the cookie offset num [length num] command.

You specify the offset in bytes, counting from the first byte of the cookie value and the length (also in bytes) that specifies the portion of the cookie that you are using to maintain the sticky connection. These values are stored in the sticky tables.

The offset and length can vary from 0 to 4000 bytes. If the cookie value is longer than the offset but shorter than the offset plus the length of the cookie, the CSM-S sticks the connection based on that portion of the cookie after the offset.

This example shows how to specify set the cookie offset and length:
Cat6k-1# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Cat6k-1(config)# module csm 4
Cat6k-1(config-module-csm)# sticky 20 cookie SESSION_ID
Cat(config-slb-sticky-cookie)# cookie offset 10 length 6
URL-Learn

The URL-learn cookie sticky feature allows the CSM-S to capture the session information of the set-cookie field or cookies embedded in URLs. The CSM-S creates a sticky table entry based on the value of a specified cookie embedded in the set-cookie HTTP header of the server's response.

When URL-learn is configured, the CSM-S can learn the cookie value in three different ways:

•Cookie message in the server to client direction

•Cookie in a client request

•Cookie value embedded in the URL

The behaviors in the first two bullets are already supported by the standard dynamic cookie learning feature, and the behavior in the last bullet is added with the URL-learn feature.

In most cases, the client then returns the same cookie value in a subsequent HTTP request. The CSM-S sticks the client to the same server based on that matching value. Some clients, however, disable cookies in their browser making this type of cookie sticky connection impossible. With the new URL cookie learn feature, the CSM-S can extract the cookie name and value embedded in the URL string. This feature works only if the server has embedded the cookie into the URL link in the web page.

If the client's request does not carry a cookie, the CSM-S looks for the session ID string (?session-id=) configured on the CSM-S. The value associated with this string is the session ID number that the CSM-S looks for in the cache. The session ID is matched with the server where the requested information is located and the client's request is sent.

Because the session cookie and the URL session ID may be different, the Cisco IOS sticky id cookie name command was updated. The example in this section shows the correct syntax.

Note The offset and length clauses were included in this updated command to support the cookie sticky offset feature in this release. See the "Cookie Sticky Offset and Length" section.

Depending on client and server behavior and the sequence of frames, the same cookie value may appear in the standard HTTP cookies appearing in the HTTP cookie, set-cookie headers, or cookies embedded in URLs. The name of a cookie may be different from the URL depending on whether the cookie is embedded in a URL or appears in an HTTP cookie header. The use of a different name for the cookie and the URL occurs because these two parameters are configurable on the server and are very often set differently. For example, the set-cookie name might be as follows:
Set-Cookie: session_cookie = 123
The URL might be as follows:
http://www.example.com/?session-id=123
The name field in the sticky command specifies the cookie name that appears in the cookie headers. The secondary session_id clause added to this command specifies the corresponding cookie name that appears in the URL.

This example shows how to configure the URL learning feature:
Cat6k-1# configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Cat6k-1(config)# module csm 4
Cat6k-1(config-module-csm)# sticky 30 cookie session_cookie
Cat(config-slb-sticky-cookie)# cookie secondary session-id
Cat(config-slb-sticky-cookie)#
Configuring Route Health Injection

These sections describe how to configure route health injection (RHI):

•Understanding RHI

•Configuring RHI for Virtual Servers

Understanding RHI

These sections describe the RHI:

•RHI Overview

•Routing to VIP Addresses Without RHI

•Routing to VIP Addresses With RHI

•Understanding How the CSM-S Determines VIP Availability

•Understanding Propagation of VIP Availability Information

RHI Overview

RHI allows the CSM-S to advertise the availability of a VIP address throughout the network. Multiple CSM-S devices with identical VIP addresses and services can exist throughout the network. One CSM-S can override the server load-balancing services over the other devices if the services are no longer available on the other devices. One CSM-S also can provide the services because it is logically closer to the client systems than other server load-balancing devices.

Note RHI is restricted to intranets because the CSM-S advertises the VIP address as a host route and most routers do not propagate the host-route information to the Internet.

To enable RHI, configure the CSM-S to do the following:

•Probe real servers and identify available virtual servers and VIP addresses

•Advertise accurate VIP address availability information to the MSFC whenever a change occurs

Note At startup with RHI enabled, the CSM-S sends a message to the MSFC as each VIP address becomes available.

The MSFC periodically propagates the VIP address availability information that RHI provides.

Note RHI is normally restricted to intranets; for security reasons, most routers do not propagate host-route information to the Internet.

Routing to VIP Addresses Without RHI

Without RHI, traffic reaches the VIP address by following a route to the client VLAN to which the VIP address belongs. When the CSM-S starts up, the MSFC creates routes to client VLANs in its routing table and shares this route information with other routers. To reach the VIP, the client systems rely on the router to send the requests to the network subnet address where the individual VIP address lives.

If the subnet or segment is reachable but the virtual servers on the CSM-S at this location are not operating, the requests fail. Other CSM-S devices can be at different locations. However, the routers send the requests based on the logical distance to the subnet only.

Without RHI, traffic is sent to the VIP address without any verification that the VIP address is available. The real servers attached to the VIP might not be active.

Note By default, the CSM-S will not advertise the configured VIP addresses.

Routing to VIP Addresses With RHI

With RHI, the CSM-S sends advertisements to the MSFC when VIP addresses become available and withdraws advertisements for VIP addresses that are no longer available. The router looks in the routing table to find the path information it needs to send the request from the client to the VIP address. When the RHI feature is turned on, the advertised VIP address information is the most specific match. The request for the client is sent through the path where it reaches the CSM-S with active VIP services.

When multiple instances of a VIP address exist, a client router receives the information it needs (availability and hop count) for each instance of a VIP address, allowing it to determine the best available route to that VIP address. The router chooses the path where the CSM-S is logically closer to the client system.

Note With RHI, you must also configure probes because the CSM-S determines if it can reach a given VIP address by probing all the real servers that serve its content. After determining if it can reach a VIP address, the CSM-S shares this availability information with the MSFC. The MSFC, in turn, propagates this VIP availability information to the rest of the intranet.

Understanding How the CSM-S Determines VIP Availability

For the CSM-S to determine if a VIP is available, you must configure a probe (HTTP, ICMP, Telnet, TCP, FTP, SMTP, or DNS) and associate it with a server farm. When probes are configured, the CSM-S performs these checks:

•Probes all real servers on all server farms configured for probing

•Identifies server farms that are reachable (have at least one reachable real server)

•Identifies virtual servers that are reachable (have at least one reachable server farm)

•Identifies VIPs that are reachable (have at least one reachable virtual server)

Understanding Propagation of VIP Availability Information

With RHI, the CSM-S sends advertisement messages to the MSFC containing the available VIP addresses. The MSFC adds an entry in its routing table for each VIP address it receives from the CSM-S. The routing protocol running on the MSFC sends routing table updates to other routers. When a VIP address becomes unavailable, its route is no longer advertised, the entry times out, and the routing protocol propagates the change.

Note For RHI to work on the CSM-S, the MSFC in the chassis in which the CSM-S resides must run Cisco IOS Release 12.1.7(E) or later releases and must be configured as the client-side router.

Configuring RHI for Virtual Servers

To configure RHI for the virtual servers, perform these steps:

Step 1 Verify that you have configured the VLANs. See Chapter 4, "Configuring VLANs."

Step 2 Associate the probe with a server farm. See the "Configuring Probes for Health Monitoring" section on page 11-1.

Step 3 Configure the CSM-S to probe real servers. See the "Configuring Probes for Health Monitoring" section on page 11-1.

Step 4 Enter the advertise active SLB virtual server command to enable RHI for each virtual server:
Router(config-module-csm)# vserver virtual_server_name
Router(config-slb-vserver)# advertise active
This example shows how to enable RHI for the virtual server named vserver1:
Router(config-module-csm)# vserver vserver1 
Router(config-slb-vserver)# advertise active
Environmental Variables

You can enable the environmental variables in the configuration with the variable name string command. Table 10-1 describes the CSM-S environmental values.

Table 10-1 CSM-S Environmental Values

Name

Default

Valid Values

Description

ARP_INTERVAL

300

Integer (15 to 31536000)

Time (in seconds) between ARP requests for configured hosts.

ARP_LEARNED_INTERVAL

14400

Integer (60 to 31536000)

Time (in seconds) between ARP requests for learned hosts.

ARP_GRATUITOUS_INTERVAL

15

Integer (10 to 31536000)

Time (in seconds) between gratuitous ARP requests.

ARP_RATE

10

Integer (1 to 60)

Seconds between ARP retries.

ARP_RETRIES

3

Integer (2 to 15)

Count of ARP attempts before flagging a host as down.

ARP_LEARN_MODE

1

Integer (0 to 1)

Indicates whether the CSM-S learns MAC addresses on responses only (0) or all traffic (1).

ARP_REPLY_FOR_NO_INSERVICE_VIP

D

0

Integer (0 to 1).

ADVERTISE_RHI_FREQ

10

Integer (1 to 65535)

Frequency in second(s) that the CSM-S uses to check for RHI updates.

AGGREGATE_BACKUP_SF_STATE_TO_VS

0

Integer (0 to 1)

Specifies whether to include the operational state of a backup server farm into the state of a virtual server.

COOKIE_INSERT_EXPIRATION_DATE

Fri, 1
Jan 2010 01:01:50 GMT

String (2 to 63 chars)

Configures the expiration time and date for the HTTP cookie inserted by the CSM-S.

DEST_UNREACHABLE_MASK

65535

Integer (0 to 65535)

Bitmask defining which ICMP destination unreachable codes are to be forwarded.

FT_FLOW_REFRESH_INT

60

Integer (1 to 65535)

Interval for the fault-tolerant slow path flow refresh in seconds.

HTTP_CASE_SENSITIVE_MATCHING

1

Integer (0 to 1)

Specifies whether the URL (cookie, header) matching and sticky are to be case sensitive.

HTTP_URL_COOKIE_DELIMITERS

/?&#+

String (1 to 64 chars)

Configures the list of delimiter characters for cookies in the URL string.

MAX_PARSE_LEN_MULTIPLIER

1

Integer (1 to 16)

Multiplies the configured max-parse-len by this amount.

NAT_CLIENT_HASH_SOURCE_PORT

0

Integer (0 to 1)

Specifies whether to use the source port to pick client NAT IP address.

ROUTE_UNKNOWN_FLOW_PKTS

0

Integer (0 to 1)

Specifies whether to route non-SYN packets that do not match any existing flows.

NO_RESET_UNIDIRECTIONAL_FLOWS

0

Integer (0 to 1)

Specifies, if set, that unidirectional flows do not be reset when timed out.

SWITCHOVER_RP_ACTION

0

Integer (0 to 1)

Specifies whether to recover (0) or halt/reboot (1) after a supervisor engine route processor switchover occurs.

SWITCHOVER_SP_ACTION

0

Integer (0 to 1)

Specifies whether to recover (0) or halt/reboot (1) after a supervisor engine switch processor switchover occurs.

SYN_COOKIE_INTERVAL

3

Integer (1 to 60)

Specifies the interval, in seconds, at which a new syn-cookie key is generated.

SYN_COOKIE_THRESHOLD

5000

Integer (0 to 1048576)

Specifies the threshold (in number of pending sessions) at which syn-cookie is engaged.

TCP_MSS_OPTION

1460

Integer (1 to 65535)

Specifies the maximum segment size (MSS) value sent by CSM-S for Layer 7 processing.

TCP_WND_SIZE_OPTION

8192

Integer (1 to 65535)

Specifies the window size value sent by CSM-S for Layer 7 processing.

VSERVER_ICMP_ALWAYS_RESPOND

false

String (1 to 5 chars)

If "true," respond to ICMP probes regardless of virtual server state.

XML_CONFIG_AUTH_TYPE

Basic

String (5 to 6 chars)

Specifies the HTTP authentication type for xml-config: Basic or Digest.

This example shows how to display the environmental variables in the configuration:
Router# show mod csm 5 variable
variable                        value
----------------------------------------------------------------
ARP_INTERVAL                    300
ARP_LEARNED_INTERVAL            14400
ARP_GRATUITOUS_INTERVAL         15
ARP_RATE                        10
ARP_RETRIES                     3
ARP_LEARN_MODE                  1
ARP_REPLY_FOR_NO_INSERVICE_VIP  0
ADVERTISE_RHI_FREQ              10
AGGREGATE_BACKUP_SF_STATE_TO_VS 0
DEST_UNREACHABLE_MASK           0xffff
FT_FLOW_REFRESH_INT             60
GSLB_LICENSE_KEY                (no valid license)
HTTP_CASE_SENSITIVE_MATCHING    1
MAX_PARSE_LEN_MULTIPLIER        1
NAT_CLIENT_HASH_SOURCE_PORT     0
ROUTE_UNKNOWN_FLOW_PKTS         0
NO_RESET_UNIDIRECTIONAL_FLOWS   0
SYN_COOKIE_INTERVAL             3
SYN_COOKIE_THRESHOLD            5000
TCP_MSS_OPTION                  1460
TCP_WND_SIZE_OPTION             8192
VSERVER_ICMP_ALWAYS_RESPOND     false
XML_CONFIG_AUTH_TYPE            Basic
Cat6k-2#
To display all information for the current set of environmental variables in the configuration, use the show module csm slot variable [detail] command as follows:
Cat6k-2# show mod csm 5 variable detail
Name:ARP_INTERVAL  Rights:RW
Value:300
Default:300
Valid values:Integer (15 to 31536000)
Description:
Time (in seconds) between ARPs for configured hosts
Name:ARP_LEARNED_INTERVAL  Rights:RW
Value:14400
Default:14400
Valid values:Integer (60 to 31536000)
Description:
Time (in seconds) between ARPs for learned hosts
Name:ARP_GRATUITOUS_INTERVAL  Rights:RW
Value:15
Default:15
Valid values:Integer (10 to 31536000)
Description:
Time (in seconds) between gratuitous ARPs
Name:ARP_RATE  Rights:RW
Value:10
Default:10
Valid values:Integer (1 to 60)
Description:
Seconds between ARP retries
Name:ARP_RETRIES  Rights:RW
Value:3
Default:3
Valid values:Integer (2 to 15)
Description:
Count of ARP attempts before flagging a host as down
Name:ARP_LEARN_MODE  Rights:RW
Value:1
Default:1
Valid values:Integer (0 to 1)
Description:
Indicates whether CSM-S learns MAC address on responses only (0) or all traffic (1)
Name:ARP_REPLY_FOR_NO_INSERVICE_VIP  Rights:RW
Value:0
Default:0
Valid values:Integer (0 to 1)
Description:
Whether the CSM-S would reply to ARP for out-of-service vserver
Name:ADVERTISE_RHI_FREQ  Rights:RW
Value:10
Default:10
Valid values:Integer (1 to 65535)
Description:
The frequency in second(s) the CSM-S will check for RHI updates
Name:AGGREGATE_BACKUP_SF_STATE_TO_VS  Rights:RW
Value:0
Default:0
Valid values:Integer (0 to 1)
Description:
Whether to include the operational state of a backup serverfarm into the state of a 
virtual server
Name:DEST_UNREACHABLE_MASK  Rights:RW
Value:0xffff
Default:65535
Valid values:Integer (0 to 65535)
Description:
Bitmask defining which ICMP destination unreachable codes are to be forwarded
Name:FT_FLOW_REFRESH_INT  Rights:RW
Value:60
Default:60
Valid values:Integer (1 to 65535)
Description:
FT slowpath flow refresh interval in seconds
Name:GSLB_LICENSE_KEY  Rights:RW
Value:(no valid license)
Default:(no valid license)
Valid values:String (1 to 63 chars)
Description:
License key string to enable GSLB feature
Name:HTTP_CASE_SENSITIVE_MATCHING  Rights:RW
Value:1
Default:1
Valid values:Integer (0 to 1)
Description:
Whether the URL (Cookie, Header) matching and sticky to be case sensitive
Name:MAX_PARSE_LEN_MULTIPLIER  Rights:RW
Value:1
Default:1
Valid values:Integer (1 to 16)
Description:
Multiply the configured max-parse-len by this amount
Name:NAT_CLIENT_HASH_SOURCE_PORT  Rights:RW
Value:0
Default:0
Valid values:Integer (0 to 1)
Description:
Whether to use the source port to pick client NAT IP address
Name:ROUTE_UNKNOWN_FLOW_PKTS  Rights:RW
Value:0
Default:0
Valid values:Integer (0 to 1)
Description:
Whether to route non-SYN packets that do not matched any existing flows
Name:NO_RESET_UNIDIRECTIONAL_FLOWS  Rights:RW
Value:0
Default:0
Valid values:Integer (0 to 1)
Description:
If set, unidirectional flows will not be reset when timed out
Name:SYN_COOKIE_INTERVAL  Rights:RW
Value:3
Default:3
Valid values:Integer (1 to 60)
Description:
The interval, in seconds, at which a new syn-cookie key is generated
Name:SYN_COOKIE_THRESHOLD  Rights:RW
Value:5000
Default:5000
Valid values:Integer (0 to 1048576)
Description:
The threshold (in number of pending sessions) at which syn-cookie is engaged
Name:TCP_MSS_OPTION  Rights:RW
Value:1460
Default:1460
Valid values:Integer (1 to 65535)
Description:
Maximum Segment Size (MSS) value sent by CSM-S for L7 processing
Name:TCP_WND_SIZE_OPTION  Rights:RW
Value:8192
Default:8192
Valid values:Integer (1 to 65535)
Description:
Window Size value sent by CSM-S for L7 processing
Name:VSERVER_ICMP_ALWAYS_RESPOND  Rights:RW
Value:false
Default:false
Valid values:String (1 to 5 chars)
Description:
If "true" respond to ICMP probes regardless of vserver state
Name:XML_CONFIG_AUTH_TYPE  Rights:RW
Value:Basic
Default:Basic
Valid values:String (5 to 6 chars)
Description:
HTTP authentication type for xml-config:Basic or Digest
Configuring Persistent Connections

The CSM-S allows HTTP connections to be switched based on a URL, cookies, or other fields contained in the HTTP header. Persistent connection support in the CSM-S allows for each successive HTTP request in a persistent connection to be switched independently. As a new HTTP request arrives, it may be switched to the same server as the prior request, it may be switched to a different server, or it may be reset to the client preventing that request from being completed.

As of software release 2.1(1), the CSM-S supports HTTP 1.1 persistence. This feature allows browsers to send multiple HTTP requests on a single persistent connection. After a persistent connection is established, the server keeps the connection open for a configurable interval, anticipating that it may receive more requests from the same client. Persistent connections eliminate the overhead involved in establishing a new TCP connection for each request.

HTTP 1.1 persistence is enabled by default on all virtual servers configured with Layer 7 policies. To disable persistent connections, enter the no persistent rebalance command. To enable persistent connections, enter the persistent rebalance command.

This example shows how to configure persistent connections:
Router# configure terminal
Enter configuration commands, one per line.  End with
CNTL/Z.
Router(config)# mod csm 2
!!! configuring serverfarm 
Router(config-module-csm)# serverfarm sf3
Router(config-slb-sfarm)# real 10.1.0.105
Router(config-slb-real)# inservice
!!! configuring vserver
Router(config-slb-real)# vserver vs3
Router(config-slb-vserver)# virtual 10.1.0.83 tcp 80
Router(config-slb-vserver)# persistent rebalance 
Router(config-slb-vserver)# serverfarm sf3
Router(config-slb-vserver)# inservice
Router(config-slb-vserver)# end
HTTP Header Insert

The HTTP header insert feature provides the CSM-S with the ability to insert information, such as the client's IP address, into the HTTP header. This feature is useful in situations where the CSM-S is performing source NAT and the application on the server side still requires visibility to the original source IP.

The CSM-S can insert the source IP address from the client into the header in the client-to-server direction.

Use the insert protocol http header name header-value value command to insert information into the HTTP header.

•name—Literal name of the generic field in the HTTP header. The name is a string with a range from 1 to 63 characters.

•value—Specifies the literal header value string to insert in the request.

You can also use the %is and %id special parameters for the header values. The %is value inserts the source IP into the HTTP header and the %id value inserts the destination IP into the header. Each special parameter may only be specified once per header map.

Note A header map may contain multiple insert headers. If you insert header values that are made of multiple keywords that include spaces, you must use double quotes around the entire expression.

When configuring HTTP header insert, you must use a header map and a policy. You cannot use the default policy for HTTP header insert to work.

This example shows how to specify header fields and values to search upon a request:
Cat6k-2(config-module-csm)# natpool TESTPOOL 10.10.110.200 10.10.110.210 netmask 
255.255.255.0
!
Cat6k-2(config-module-csm)# map HEADER-INSERT header
Cat6k-2(config-slb-map-header)# insert protocol http header Source-IP header-value %is
Cat6k-2(config-slb-map-header)# insert protocol http header User-Agent header-value 
"MyBrowser 1.0"
!
Cat6k-2(config-module-csm)# real SERVER1
Cat6k-2(config-slb-real)# address 10.10.110.10
Cat6k-2(config-slb-real)# inservice
Cat6k-2(config-module-csm)# real SERVER2
Cat6k-2(config-slb-real)# address 10.10.110.20
Cat6k-2(config-slb-real)# inservice
!
Cat6k-2(config-module-csm)# serverfarm FARM-B
Cat6k-2(config-slb-sfarm)# nat server
Cat6k-2(config-slb-sfarm)# nat client TESTPOOL
Cat6k-2(config-slb-real)# real name SERVER1
Cat6k-2(config-slb-real)# inservice
Cat6k-2(config-slb-real)# real name SERVER2
Cat6k-2(config-slb-real)# inservice
!
Cat6k-2(config-module-csm)# policy INSERT
Cat6k-2(config-slb-policy)# header-map HEADER-INSERT
Cat6k-2(config-slb-policy)# serverfarm FARM-B
!
Cat6k-2(config-module-csm)# vserver WEB
Cat6k-2(config-slb-vserver)# virtual 10.10.111.100 tcp www
Cat6k-2(config-slb-vserver)# persistent rebalance
Cat6k-2(config-slb-vserver)# slb-policy INSERT
Cat6k-2(config-slb-vserver)# inservice
Configuring Global Server Load Balancing

This section contains the CSM global server load-balancing (GSLB) advanced feature set option and instructions for its use. You should review the terms of the software license agreement in the "Licenses" section on page xxvi in the Preface and on the back of the title page carefully before using the advanced feature set option.

Note By downloading or installing the software, you are consenting to be bound by the license agreement. If you do not agree to all of the terms of this license, then do not download, install, or use the software.

Using the GSLB Advanced Feature Set Option

To enable GSLB, perform this task in privileged mode:
Command

Purpose
Router# config t
Router(config)# mod csm 5
Enters the configuration mode and enters CSM-S configuration mode for the specific CSM-S (for example, module 5, as used here).
Router(config-module-csm)# variable name value
Enables GSLB by using the name and value provided as follows:
Name= ¹
Value=
Router(config-module-csm)# exit
Router (config)# write mem
Exits CSM-S module configuration mode and saves the configuration changes.
Router#:hw-module slot number reset
Reboots your CSM-S to activate changes.
¹GSLB requires a separately purchased license. To purchase your GSLB license, contact your Cisco representative.
Table 10-2 lists the GSLB environmental values used by the CSM-S.

Table 10-2 GSLB Environmental Values

Name

Default

Valid Values

Description

GSLB_LICENSE_KEY

(no valid license)

String (1 to 63 chars)

License key string to enable GSLB feature.

GSLB_KALAP_UDP_PORT

5002

Integer (1 to 65535)

Specifies the GSLB KAL-AP UDP port number.

GSLB_KALAP_PROBE_FREQ

45

Integer (45 to 65535)

Specifies the frequency of the GSLB KAL-AP probes.

GSLB_KALAP_PROBE_RETRIES

3

Integer (1 to 65535)

Specifies the maximum retries for GSLB KAL-AP probes.

GSLB_ICMP_PROBE_FREQ

45

Integer (45 to 65535)

Specifies the frequency of the GSLB ICMP probes.

GSLB_ICMP_PROBE_RETRIES

3

Integer (1 to 65535)

Specifies the maximum retries for GSLB ICMP probes.

GSLB_HTTP_PROBE_FREQ

45

Integer (45 to 65535)

Specifies the frequency of the GSLB HTTP probes.

GSLB_HTTP_PROBE_RETRIES

3

Integer (1 to 65535)

Specifies the maximum retries for the GSLB HTTP probes.

GSLB_DNS_PROBE_FREQ

45

Integer (45 to 65535)

Specifies the frequency of the GSLB DNS probes.

GSLB_DNS_PROBE_RETRIES

3

Integer (1 to 65535)

Specifies the maximum retries for GSLB DNS probes.

Configuring GSLB

GSLB performs load balancing between multiple, dispersed hosting sites by directing client connections through DNS to different server farms and real servers based on load availability. GSLB is performed using access lists, maps, server farms, and load-balancing algorithms. Table 10-3 provides an overview of what is required for a GSLB configuration on the CSM-S.

Table 10-3 GSLB Operations

Client Request (From)

Domain (For)

Server farm (To)

Algorithm (Method)

Access lists can be used to filter incoming DNS requests, and policies are used to associate the configured maps, client groups, and server farms for incoming DNS requests.

A map is configured to specify the domain names that client requests must match. Regular expression syntax is supported.

For example, domain names are cnn.com or yahoo.com that a client request must be matched against. If the domain name matches the specified map of a policy, the primary server farm is queried for a real server to respond to the request.

A server farm specifies a group of real servers where information is located that satisfies the client's request.

The GSLB probe is available for determining the availability of a target real server, using the probe type configured on the real server.

GSLB server farm predictors are round-robin least load, ordered list, hash address source, hash domain, and hash domain address source.

Figure 10-1 shows a basic configuration for GSLB.

Figure 10-1 Global Server Load Balancing Configuration

In Figure 10-1, these guidelines apply to the configuration task and example:

•CSM-S 1 does both GSLB and SLB, while CSM-S 2 and CSM-S 3 only do SLB.

•CSM-S 1 has both a virtual server for SLB (where the real servers in the server farm are the IP addresses of the local servers) and a virtual server for GSLB.

•The DNS policy uses a primary server farm (where one of the real servers is local and the other two real servers are virtual servers configured on CSM-S 2 and CSM-S 3).

•Probes should be added for both the remote locations and the local real and virtual server.

•DNS requests sent to a CSM-S 1 management IP address (a CSM-S 1 VLAN address or alias IP) will receive as a response one of the three real server IPs configured in the server farm GSLBFARM.

To configure GSLB, perform this task:
Command

Purpose
Step 1
Router(config-slb-vserver)# 
serverfarm serverfarm-name
Creates a server farm to associate with the virtual server.
Step 2
Router(config-module-csm)# 
vserver virtserver-name 
Identifies a virtual server for SLB on CSM-S 1 and enters the virtual server submode.
Step 3
Router(config-slb-vserver)# 
virtual ip-address [ip-mask] 
protocol port-number [service 
ftp]
Configures the virtual server attributes.
Step 4
Router(config-slb-vserver)# 
inservice
Enables the virtual server for load balancing.
Step 5
Router(config-module-csm)# 
vserver virtserver-name dns
Identifies a virtual server for GSLB and enters the virtual server submode.
Step 6
Router(config-slb-vserver)# 
dns-policy [group group-id] 
[netmask ip-netmask]
Ensures that connections from the same client use the same server farm.
Step 7
Router(config-slb-vserver)# 
inservice
Enables the virtual server for GSLB.
Step 8
Router(config-module-csm)# 
serverfarm GSLBFARM dns-vip
Creates and names the GSLBFARM server farm (which is actually a forwarding policy) and enters server farm configuration mode.
Step 9
Router(config-slb-sfarm)# 
predictor hash address source
Configures the hash address source for the load-balancing predictor for the server farm.
Step 10
Router(config-module-csm)# 
real ip-addres
Identifies the alias IP address of the real server and enters real server configuration submode.
Step 11
Router(config-slb-real)# 
inservice 
Enables the virtual server for load balancing.
Step 12
Router(config-module-csm)# 
map dns-map-name dns
Configures a DNS map.
Step 13
Router(config-dns-map)# match 
protocol dns domain name
Adds a DNS name to the DNS map.
Step 14
Router(config-module-csm)# 
policy policy name
Configures a policy.
Step 15
Router(config-slb-policy)# 
dns map map_name
Adds the DNS map attribute to the policy.
Step 16
Router(config-slb-policy)# 
serverfarm primary-serverfarm 
[backup sorry-serverfarm 
[sticky]]
Associate the server farm with the policy.
Step 17
Router(config-module-csm)# 
vserver virtserver-name 
Configures a virtual server on CSM-S 2 and enters the virtual server submode.
Step 18
Router(config-slb-vserver)# 
virtual ip-address [ip-mask] 
protocol port-number [service 
ftp]
Configures the virtual server attributes.
Step 19
Router(config-slb-vserver)# 
serverfarm serverfarm-name
Associates a server farm with the virtual server.
Step 20
Router(config-slb-vserver)# 
inservice
Enables the virtual server for load balancing.
Step 21
Router(config-module-csm)# 
vserver virtserver-name 
Configures a virtual server on CSM-S 3 and enters the virtual server submode.
Step 22
Router(config-slb-vserver)# 
virtual ip-address [ip-mask] 
protocol port-number [service 
ftp]
Configures the virtual server attributes.
Step 23
Router(config-slb-vserver)# 
serverfarm serverfarm-name
Associates a server farm with the virtual server.
Step 24
Router(config-slb-vserver)# 
inservice
Enables the virtual server for load balancing.
This example shows how to configure GSLB:

On CSM1:
Router(config-module-csm)# serverfarm WEBFARM
Router(config-slb-sfarm)# predictor round-robin
Router(config-slb-sfarm)# real 3.5.5.5
Router(config-slb-real)# inservice
Router(config-slb-sfarm)# real 3.5.5.6
Router(config-slb-real)# inservice
Router(config-slb-real)# exit
Router(config-slb-sfarm)# exit
Router(config-module-csm)# vserver WEB
Router(config-slb-vserver)# virtual 10.10.10.10 tcp www
Router(config-slb-vserver)# serverfarm WEBFARM
Router(config-slb-vserver)# inservice
Router(config-module-csm)# serverfarm GSLBSERVERFARM dns-vip
Router(config-slb-sfarm)# predictor round-robine
Router(config-slb-sfarm)# real 10.10.10.10
Router(config-slb-real)# inservice
Router(config-slb-real)# exit
Router(config-slb-sfarm)# real 20.20.20.20
Router(config-slb-real)# inservice
Router(config-slb-real)# exit
Router(config-slb-sfarm)# real 30.30.30.30
Router(config-slb-real)# inservice
Router(config-slb-real)# exit
Router(config-module-csm)# map MAP1 dns
Router(config-dns-map)# match protocol dns domain foobar.com
Router(config-dns-map)# exit
Router(config-module-csm)# policy DNSPOLICY dns
Router(config-slb-policy)# dns map MAP1
Router(config-slb-policy)# serverfarm primary GSLBSERVERFARM ttl 20 responses 1
Router(config-slb-policy)# exit
Router(config-module-csm)# vserver DNSVSERVER dns
Router(config-slb-vserver)# dns-policy DNSPOLICY
Router(config-slb-vserver)# inservice
On CSM-S 2:
Router(config-module-csm)# serverfarm WEBFARM
Router(config-slb-sfarm)# 