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CCDP Self-Study: Designing High-Availability Services

Chapter Description

Cisco IOS high-availability technologies provide network redundancy and fault tolerance. Reliable network devices, redundant hardware components with automatic failover, and protocols like Hot Standby Router Protocol (HSRP) are used to maximize network uptime. This chapter will help you get a handle on high-availability technologies.

Case Study: OCSIC Bottling Company

The purpose of this case study is to practice the key design skills discussed in this chapter. For this project, you must revisit the earlier design for OCSIC Bottling Company and ensure that the Campus Infrastructure, Server Farm, WAN, Remote Access, and Internet Connectivity modules are highly available. Specifically, you have been asked to develop a high-availability design for the Campus Infrastructure module, and to develop a high-availability strategy for the Server Farm, WAN, Remote Access, and finally, the Internet Connectivity modules. For each identified component of the design, you are required to provide justification for our decision. The justification will provide an explanation for the options considered, and the reason behind choosing the selected option.

High-Availability Design for the Campus Infrastructure Module

Table 5-7 summarizes one possible set of design decisions that meet the OCSIC Bottling Company's requirements for high-availability solutions for the headquarters' campus network.

Table 5-7 Design Decisions Made to Develop a High-Availability Strategy for the Headquarters Campus Network

Design Question

Decision

Justification

Which devices should be fault tolerant?

None

It is deemed not cost effective to add fault-tolerant devices in the campus network.

Which devices should be redundant?

Cisco Catalyst 3550-12G is a good candidate for the distribution layer.

For every Catalyst 3550-12G in the design, a second 3550-12G switch is added to provide device redundancy.

Catalyst 4006s with Supervisor IIIs, and two 8-port GB Ethernet (4908G) modules would be good candidates for the backbone layer.

Device redundancy provides high availability as needed in the campus network.

Which links should be redundant?

Catalyst 3524 stacks have redundant links to the Building Distribution switches.

Redundant links provide backup in case of a link failure.

What spanning-tree implementation and root devices are required?

Spanning-tree root at the Building Distribution switches using RSTP/MST.

For simplicity, the Building Distribution is used as the STP root because it provides a logical break between the data link and network layers.

What is the router availability strategy?

HSRP

HSRP implemented in the multilayer switches provides high availability.


High-Availability Strategy for the Server Farm Module

Table 5-8 summarizes one possible set of design decisions that meet the OCSIC Bottling Company's requirements for high-availability solutions for the Server Farm module.

Table 5-8 Design Decisions Made to Develop a High-Availability Strategy for the Server Farm Module

Design Question

Decision

Justification

Which devices should be fault tolerant?

All devices

Fault tolerance is critical in the Server Farm module.

Which devices should be redundant?

None

Fault tolerance is preferred to device redundancy in the Server Farm module.

Which links should be redundant?

Redundant links throughout the Server Farm module.

Redundant links are required for high availability.

What spanning-tree implementation and root devices are required?

Spanning-tree root at the Server Distribution switches using RSTP/MST.

For simplicity, the Server Distribution is used as the STP root because it provides a logical break between the data link and network layers.

What is the router availability strategy?

HSRP

HSRP implemented in the multilayer switches provides high availability.


High-Availability Strategy for the WAN Module

Table 5-9 summarizes one possible set of design decisions that meet the OCSIC Bottling Company's requirements for high-availability solutions for the WAN module.

Table 5-9 Design Decisions Made to Develop a High-Availability Strategy for the WAN Module

Design Question

Decision

Justification

Which devices should be fault tolerant?

None

Fault tolerance is not cost effective in the WAN module.

Which devices should be redundant?

The module should have two Cisco 3640 routers for WAN redundancy.

The second Cisco 3640 WAN router provides the necessary high availability for the WAN module.

Which links should be redundant?

Redundant links to the Edge Distribution module.

Redundant links provide backup in case of a link failure.

What spanning-tree implementation and root devices are required?

None

Not applicable

What is the router availability strategy?

HSRP will run on the Cisco 3640 routers in the WAN module.

HSRP provides high availability.


High-Availability Strategy for the Remote Access Module

Table 5-10 summarizes one possible set of design decisions that meet the OCSIC Bottling Company's requirements for high-availability solutions for the Remote Access module.

Table 5-10 Design Decisions Made to Develop a High-Availability Strategy for the Remote Access Module

Design Question

Decision

Justification

Which devices should be fault tolerant?

None

Fault tolerance is not cost effective in the Remote Access module.

Which devices should be redundant?

None

Device redundancy is not cost effective in the Remote Access module.

Which links should be redundant?

Redundant links to the Edge Distribution module.

Redundant links provide backup in case of a link failure.

What spanning-tree implementation and root devices are required?

None

Not applicable

What is the router availability strategy?

HSRP

HSRP provides high availability.


High-Availability Strategy for the Internet Connectivity Module

Table 5-11 summarizes one possible set of design decisions that meet the OCSIC Bottling Company's requirements for high-availability solutions for the Internet Connectivity module.

Table 5-11 Design Decisions Made to Develop a High-Availability Strategy for the Internet Connectivity Module

Design Question

Decision

Justification

Which devices should be fault tolerant?

None

Fault tolerance is not cost effective in the Internet Connectivity module.

Which devices should be redundant?

None

Device redundancy is not cost effective in the Internet Connectivity module.

Which links should be redundant?

Redundant links to the Edge Distribution module.

Redundant links provide backup in case of a link failure.

What spanning-tree implementation and root devices are required?

None

Not applicable

What is the router availability strategy?

HSRP

HSRP provides high availability.


Revised Network Diagrams

Figures 5-7 and 5-8 show the updated network diagrams to reflect the high-availability strategies presented.

Figure 7Figure 5-7 Revised Network Diagram for the Headquarters' Location with High-Availability Services

Figure 8Figure 5-8 A Network Diagram for the WAN with Redundant Links for Load Sharing and High Availability