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Overview

Overview

The Catalyst 6000 family Content Switching Module (CSM) provides high-performance server load balancing (SLB) between network devices and server farms based on Layer 4 through Layer 7 packet information. Server farms are groups of real servers.

Server farms that are represented as virtual servers can improve scalability and availability of services for your network. You can add new servers and remove failed or existing servers at any time without affecting the virtual server's availability.

Clients connect to the CSM by supplying the virtual IP (VIP) address of the virtual server. When a client initiates a connection to the virtual server, the CSM chooses a real server (a physical device that is assigned to a server farm) for the connection based on configured load-balancing algorithms and policies (access rules). Policies manage traffic by defining where to send client requests for information.

Sticky connections limit traffic to individual servers by allowing multiple connections from the same client to stick to the same real server using source IP addresses, source IP subnets, cookies, and the secure socket layer (SSL) or by redirecting these connections using the Hypertext Transfer Protocol (HTTP) requests.

Note   The CSM runs on Cisco IOS Release 12.1(6)E or later. If you are using a Supervisor Engine 2, you must use Cisco IOS Release 12.1(8a)EX or later. To use the CSM Release 2.1(1), you must be running Cisco IOS Release 12.1(8a)EX or later.
Release 2.2(1) will run with Cisco IOS Release 12.1(8a)EX. However, those features new in CSM Release 2.2(1) will not be available. To use the features added in CSM Release 2.2(1), you must be running Cisco IOS Release 12.1(11b)E or later.
Caution   The WS-X6066-SLB-APC Content Switching Module is not fabric enabled.

These sections describe the CSM:

Features

The CSM provides these enhanced features:

Table 1-1 lists the available CSM features.


Table 1-1: CSM Feature Set Description
Features
Supported Hardware
Supervisor 1A with MSFC and PFC

Supervisor 2

Supported Protocols
TCP load balancing

UDP and all common IP protocol load balancing

Support for FTP and the Real Time Streaming Protocol (RTSP)

Layer 7 Functionality
Full regular expression matching

URL and cookie switching

Generic header parsing

Miscellaneous Functionality
Multiple CSMs in a chassis

CSM and IOS-SLB functioning simultaneously in a chassis

HTTP 1.1 persistence (all GETs to the same server)

Full HTTP 1.1 persistence (GETs balanced to multiple servers)

Fully configurable NAT

Server initiated connections

Route health injection

Load-balancing Algorithms
Round robin

Weighted round robin

Least connections

Weighted least connections

URL hashing

Source IP hashing

Destination IP hashing

Configurable pending connection timeout

Load Balancing Supported
Server load balancing

Firewall load balancing

DNS load balancing

Stealth firewall load balancing

Transparent cache redirection

Reverse proxy cache

SSL off-loading

VPN-Ipsec load balancing

Stickiness
Cookie

SSL ID

Source IP

HTTP redirection

Redundancy
Sticky state

Full stateful failover (connection redundancy)

Health Checking
HTTP

ICMP

Telnet

TCP

FTP

SMTP

DNS

Return error code checking

Inband health checking

Management
SNMP traps

Front Panel Description

Figure 1-1 shows the CSM front panel.


Figure 1-1: Content Switching Module Front Panel


Note   The RJ-45 connector is covered by a removable plate.

Status LED

When the CSM powers up, it initializes various hardware components and communicates with the supervisor engine. The Status LED indicates the supervisor engine operations and the initialization results.

Note   For more information on the supervisor engine LEDs, refer to the Catalyst 6000 Family Module Installation Guide.

During the normal initialization sequence, the status LED changes from off to red, orange, and green. Table 1-2 describes the Status LED operation.


Table 1-2: Content Switching Module Status LED
Color Description

Off

  • The module is waiting for the supervisor engine to provide power.

  • The module is not on line.

  • The module is not receiving power, which could be caused by the following:

    • Power is not available to the CSM.

    • Module temperature is over the limit1.

Red

  • The module is released from reset by the supervisor engine and is booting.

  • If the boot code fails to execute, the LED stays red after power up.

Orange

  • The module is initializing hardware or communicating with the supervisor engine.

  • A fault occurred during the initialization sequence.

  • The module has failed to download its Field Programmable Gate Arrays (FPGAs) on power up, but continues with the remainder of the initialization sequence and provides the module online status from the supervisor engine.

  • The module has not received module online status from the supervisor engine. This problem could be caused by the supervisor engine detecting a failure in an external loopback test that it issued to the CSM.

Green

  • The module is operational; the supervisor engine has provided module online status.

Green to orange

  • The module is disabled through the supervisor engine CLI 2 using the set module disable mod command.

1Enter the show environment temperature mod command to display the temperature of each of four sensors on the CSM.
2CLI = command-line interface.

RJ-45 Connector

The RJ-45 connector, which is covered by a removable plate, is used to connect a management station device or a test device. This connector is used by field engineers to perform testing and to obtain dump information.

Operation Mode

Clients and servers communicate through the CSM using Layer 2 and Layer 3 technology in a specific VLAN configuration. (See Figure 1-2.) Clients connect to the client-side VLAN and servers connect to the server-side VLAN. Servers and clients can exist on different subnets. Servers can also be located one or more Layer 3 hops away and connect to the server-side VLAN through routers.

A client sends a request to one of the module's VIP addresses. The CSM forwards this request to a server that can respond to the request. The server then forwards the response to the CSM, and the CSM forwards the response to the client.

When the client-side and server-side VLANs are on the same subnets, you can configure the CSM in single subnet (bridge) mode. For more information, see the "Configuring the Single Subnet (Bridge) Mode" section.

When the client-side and server-side VLANs are on different subnets, you can configure the CSM to operate in a secure (router) mode. For more information, see the "Configuring the Secure (Router) Mode" section.

You can set up a fault-tolerant configuration in either the secure (router) or single subnet (bridged) mode using redundant CSMs. For more information, see the "Configuring Fault Tolerance" section.

Using multiple VLANs, single subnet (bridge) mode and secure (router) mode can coexist in the same CSM.


Figure 1-2: Content Switching Module and Servers


Traffic Flow

This section describes how the traffic flows between the client and server in a CSM environment. (See Figure 1-3.)


Figure 1-3: Traffic Flow between Client and Server


Note   The numbers in Figure 1-3 correspond to the steps in the following operation procedure.

When you enter a request for information by entering a URL, the traffic flows as follows:

    1. You enter a URL. (Figure 1-3 shows www.fox.com as an example.)

    2. The client contacts a DNS server to locate the IP address associated with the URL.

    3. The DNS server sends the IP address of the virtual IP (VIP) to the client.

    4. The client uses the IP address (CSM VIP) to send the HTTP request to the CSM.

    5. The CSM receives the request with the URL, makes a load-balancing decision, and selects a server.

For example, in Figure 1-3, the CSM selects a server (X server) from the www.fox.com server pool, replacing its own VIP address with the address of the X server and forwards the traffic to the X server to allow the servers to initiate connections that do not have matching entries in the NAT configuration. If a NAT server is not specified, the VIP address remains unchanged.

    6. The CSM performs Network Address Translation (NAT).


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Posted: Mon Mar 11 15:12:44 PST 2002
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