Cisco CATALYST MEM-C6K-FLC16M Manual de usuario descargar pdf (Pagina 3)

Advanced Load Balancing

The Catalyst 4840G is a fixed-configuration SLB switch that is

based on industry-standard Cisco IOS software and, therefore,

gains all the features of this time-proven software. In addition, the

Catalyst 4840G has some key advantages with respect to network

uptime that is crucial to enterprises and ISP Web-hosting sites.

These include but are not limited to:

Dynamic Feedback Protocol

The Dynamic Feedback Protocol (DFP) is a mechanism that allows

servers to provide intelligent feedback to SLB devices such as the

Catalyst 4840G, Catalyst6000 or LocalDirector. It is used to ensure

that SLB devices do not route traffic to over-utilized applications or

servers and that traffic is sent to the correct server. Server-based

agents can use DFP to communicate application health, availability

and load to SLB devices. Advanced forms of these server agents

can provide QoS functionality, and workload management

capability. DFP is the first protocol that allows servers to provide

feedback and input into the SLB load-balancing decision. The

ability for multiple serveragents to exist on a serverplatform allows

the server to inform the SLB device whether a particular server is

either over- or under-utilized, that it should not be used for a

specified period of time, or that a particular application should take

precedence over generic applications.

HTTP Probes

While DFP provides a comprehensive feedback mechanism

between the server and the switch, often a simple poll of the

application URL will be adequate for network managers to verify

server availability. The Catalyst 4840G introduces this capability

in a ﬂexible manner via switched–based HTTP probes. In many

cases, both mechanisms can be used; DFP to tune the SLB

decision process based on the server’s operating parameters, and

HTTP probes to verify server health and content accuracy. The

HTTP probe is user-deﬁned on the Catalyst 4840G and can be

either an HTTP Get or Post, with an optional user name, user

password and URL speciﬁed. The switch will make the request at

a user-speciﬁed interval, compare the return status, and take the

appropriate action. If required, the switch can take down the

server and send Simple Network Management Protocol (SNMP)

traps to the network manager while keeping statistics of the

number of failures and the current and cumulative downtime of a

particular server. This feature ensures the maximum uptime for

servers and their hosted mission-critical applications.

SLB Redundancy

Cisco has been a leader for years in designing high-availability

networks and continues to provide innovative solutions that meet

the requirements of network managers. To provide a solution to

the redundancy requirements in the data center for SLB devices,

the Catalyst 4840 SLB switch will support both stateful and

stateless automatic fail-over. Both of these schemes are built upon

the HSRP that has been extended to provide services for SLB. As

a conﬁgurable parameter the two Catalyst 4840G switches can be

deployed in either a stateful or stateless mode. In stateless mode,

the switches communicate only via HSRP hello messages, while

in stateful mode the switches communicate via HSRP hello

messages as well as providing each other with their status

information. In the unlikely event of a switch failure, the

secondary switch would be able to take over operation of the

failed switches rebuilding the connection database. Since the

communication between the switches is via a standard Ethernet,

there are no distance limitations to this scheme and redundant

switches can be in different areas of the data center or even in

different buildings. Additionally, since the switches can have

redundant routes to their neighbors-link redundancy is also

included in this scheme—an industrial-strength, redundant design

is provided for non-stop e-commerce operations.

Firewall Probes

To ensure the reliability of the security environment, the Catalyst

4840G uses ping or HTTP probes to verify ﬁrewall health. Probes

detect ﬁrewall failures and act upon them (see HTTP probes).

Comprehensive SLB Network Management with CiscoWorks2000 and

Content Flow Manager

The Catalyst 4840G series of products are easily managed by the

powerful CiscoWorks2000 network management products. The

Essentials product suite leverages the power of the intranet with

browser-based access anywhere within the network. Network

managers can walk up to any browser console, identify who they

are via the access-control interface, and immediately begin

checking on the uptime of each device, the active software

versions that are running the Catalyst 4840G, and print a

comprehensive report. For drill-down, real-time, device status

information, network operations staff members can launch the

Cisco award-winning CiscoView application from their

fault-management station and at a glance check on the health of

the power supplies, line cards, and operational status of each port.

Monitoring server load-balancing networks, deploying the Catalyst

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