This paper documents a successful four-phase release migration process implemented by a large retail customer working closely with its Cisco® Advanced Services team. It can be used by any Cisco customer to simplify network operations and management.
Summary
When you follow a repeatable migration process, you can also benefit from reduced costs in operations, management, and training. The four phases of release migration are:
- Plan—Set goals, identify resources, profile network hardware and software, and create a preliminary schedule for migrating to new releases.
- Design—Choose new Cisco IOS® Software releases and create a strategy for migrating to them.
- Implement—Schedule and implement the migration.
- Operate—Monitor migration progress and track variations from the plan.
Using the four-phase approach, a company replaces or adds new equipment that runs Cisco IOS Software as part of a four-phase cycle instead of migrating to releases on a piecemeal basis.
Why Migrate
Well-planned migrations of Cisco IOS Software keep a network healthy during and after the migration. The primary reasons for migrating to new releases are to consolidate releases, to fix or replace releases, and to deploy a new application.
Migrate to Consolidate Releases
You may have more releases in your network than the network requires. Cisco integrates functions into new releases over time, so you can replace old releases in your network with new ones that incorporate the same features. Reducing the number of releases in your network to a minimum can simplify network operations, management, and training.
After you consolidate releases, it's easier to deploy new functions and hardware and easier to fix or upgrade obsolete releases. Network personnel learn operation and configuration procedures for a standard set of protocols and features, and they don't have to be retrained for each release.
Migrate to Fix or Replace Releases
When you require a fix or need to replace a release that has reached the end of its lifecycle, it's time to migrate to another release. Following a migration process speeds any necessary updates and simplifies the task of tracking the release versions that are running in the network.
Migrate to Deploy a New Application
New hardware, new features, or new technologies, such as IP telephony, may require you to introduce new releases into your network. Whenever you introduce change into your network, it's best to follow an established process to minimize the effect on the network. Following a process for release migration can reduce risk, speed implementation, and improve network availability. The following sections describe each of the four phases in detail.
Developing a Migration Plan
In the planning phase, identify your particular company's reasons for migration, identify resources, and profile the network and the company's business.
Determine Migration Goals
Understanding the reasons why a company wants or needs to migrate releases requires a thorough understanding of the business itself. To determine migration goals:
- Identify business requirements—Create a comprehensive profile of the facets of the business that influence migration, such as depreciation cycles, acquisition plans, needs for new network services, and attitudes toward migration.
- Determine when to migrate—Timing is important if the company is planning a corporate acquisition or replacing depreciated network equipment.
- Identify industry constraints—Find out whether the industry imposes constraints that would affect migrations. For example, pharmaceutical companies might have to adhere to procedures that affect changing processes, including changes to their network.
Identify and Finance Required Resources
First, choose a team to work on the migration and identify the necessary resources. Cisco can provide all of the skilled personnel required to plan and implement a Cisco IOS Software migration as part of a service package. The plan should include a test system that simulates your network, so that the deployment team can test migrations before upgrading the production network. Finally, create a high-level, preliminary schedule and a budget for the migration project.
Profile the Network
The network profile is important because it establishes a baseline for the migration process. Because the network is subject to change, you need to profile it on a regular basis. The network profile identifies:
- Types of network devices
- Locations of devices in the network
- Software releases running on the devices
- Key network technologies, such as wireless and voice
- Supported features that the business is using
Talk to your Cisco partner to learn more about profiling your network. Figure 1 shows a portion of a sample network profile report. Figure 1. Sample Network Profile Report
Figure 1. Sample Network Profile Report
Designing a Strategy for Migrating Releases
In the design phase, use the network profile to develop a migration strategy that includes identifying the releases to be upgraded and picking new releases for migration.
Identify Releases to Upgrade
Identify which releases should be upgraded by understanding the Cisco IOS Software release policy and tracking releases through their lifecycle. The Cisco IOS Software release policy addresses lifecycle guidelines and migration planning. The following acronyms are associated with lifecycle milestones:
- FCS—First Customer Shipment: Release is first available to customers on Cisco.com.
- EoS—End of Sale: Customers can no longer order a release from Cisco manufacturing, but maintenance releases are available to download from Software Center. An announcement six months before EoS provides advanced notice of the milestone.
- EoE—End of Engineering: Cisco no longer builds Cisco IOS Software images, no new software fixes are provided, and no new functions are added, but the Cisco Technical Assistance Center (TAC) continues to offer customer support.
- EoL—End of Life: Cisco TAC ends customer support for the release and only opens a case to recommend upgrading a customer to a newer release.
When a Cisco release approaches EoS, plan to replace it. For more information, see "Cisco IOS Software Product Lifecycle Dates & Milestones," Product Bulletin No. 2214.
Figure 2 shows that EoE schedule is up to 48 months from FCS. The EoS and EoL milestones are based on the EoE date. Cisco recommends that release review and migration planning start at 36 months.
Figure 2. Cisco IOS Software Lifecycle Time Frames
Cisco IOS Software placed on the Cisco IOS Software Center remains available for customer download for 18 months. After that it is eligible for retirement and removal from the Cisco IOS Software Center. This software retirement policy applies to T and S releases, as well as Cisco IOS Software Release 12.0S.
Cisco IOS Software on the Cisco IOS Software Center is not retired unless a viable migration path exists. A viable migration path is one that does not cross critical memory boundaries for supported hardware and, if applicable, has a similar internal or external certification. As always, Cisco IOS Software is subject to deferral at any time should a widespread, catastrophic software defect be discovered.
Software retirement is not a formal lifecycle milestone, but it does underscore the Cisco recommendation that you implement current versions of Cisco IOS Software. Cisco does not recommend new deployments of retired software.
Cisco IOS Software is retired based on its age. If the Cisco IOS Software running in a network is retired, it does not mean the software should be automatically replaced. If the software is meeting your needs, then you should continue to use it. Cisco supports retired software until it reaches the end of its lifecycle.
Regardless of its status on the Cisco IOS Software Center, Cisco recommends that you maintain copies of all Cisco IOS Software releases in your network.
Pick New Cisco IOS Software Releases
The most common reasons for migrating from Cisco IOS Software releases are to fix bugs or to add features. Determine which new features, if any, your business might require. Also, determine if you will need features supported by old releases in the new releases. Features that you use in an old release may not be available in a new release. Determine whether your business will need additional services. Software applications often require additional hardware and Cisco IOS Software migrations. A voice-over-IP (VoIP) application, for example, may require new routers that can support voice.
One of the most important tasks in migrating to new Cisco IOS Software releases is selecting the release that best meets your business and network requirements. You may have more releases in the network than necessary, and Cisco may no longer support them all. Some releases may have been installed to provide an emergency fix and are long overdue for replacement. Generally, the older the release, the harder it is to migrate to a new release. Cisco gives you a wide selection of products and technologies from which to choose and provides tools to help identify the right release for migration.
Cisco recommends that you regularly take inventory of the Cisco IOS Software releases you have deployed. Taking inventory helps to ensure that your networks are running the most current, supported releases. It also helps to keep the total number of releases deployed in customer networks to a minimum.
In general, the migration path for a Cisco IOS Software release is to the latest version of that release. The latest version incorporates the current software fixes, hardware support, and new software features. For example, the upgrade path from a maintenance release is to a new version of that maintenance release, and the upgrade path from a T release or an SG release is to a new version of the T or SG release, respectively.
To support new hardware or functions, you might need to upgrade from a maintenance release to a T release, or to a completely different family. For example, to support the latest features of the Cisco 10000 Series Router, upgrade from Cisco IOS Software Release 12.0S or 12.3XI to 12.3SB, or to support the latest features of the Cisco Catalyst® 6500 Series Switch, upgrade from Release 12.1E to 12.2SX.
Note 
Cisco IOS Software release migration is an ongoing process that takes detailed planning. You should work closely with your account managers when taking inventory of your deployed Cisco IOS Software releases and planning migration to the most current releases.
Migration Examples for T Releases
Table 1 and Table 2 describe example migration paths from current Cisco IOS Software T releases.
Table 1. Migration Paths from Cisco IOS Software Release 12.4(7)
Table 2. Migration Paths from Cisco IOS Software Release 12.4(9)T
Migration Examples for S Releases
Table 3 and Table 4 describe example migration paths from Cisco IOS Software S releases.
Table 3. Migration Paths from Cisco IOS Software Release 12.2(28)SB
Table 4. Migration Paths from Cisco IOS Software Release 12.2(18)SXF
Migration Examples for XR Releases
Table 5 describes example migration paths from current Cisco IOS Software XR releases.
Table 5. Migration Paths from Cisco IOS Software XR Releases
Check Release Availability and Outstanding Bugs
Check that the release is available when you plan to implement the migration. Open the Bug Toolkit at: http://www.cisco.com/pcgi-bin/Support/Bugtool/home.pl.
Using the Bug Toolkit, determine which bugs are open on new releases you pick for migration. What are the scenarios under which the bug surfaces? Cisco personnel may have to answer these questions.
Develop a Deployment Strategy
When migrating to new Cisco IOS Software releases, upgrade the entire network at once. An error in planning or execution can cause major network problems and disrupt business. Create a deployment strategy that tests the releases in a lab environment and then deploys releases at the edge of the network first. This limits the effect of problems to a small part of the network and simplifies the troubleshooting process. Continue this process in increments toward the network core.
Implementing Release Migrations
During the implementation phase, create a detailed migration schedule and implement the plan. The migration schedule should include information from the network profile, the new releases that replace old releases, availability dates for new releases, and start and end dates for implementing the migration.
Create a resources document that defines the tasks, shows task owners, lists resources, and sets start and end dates. Cisco Advanced Services often assists large and medium-sized firms with migration. Smaller firms get help from Cisco partners or their own consultants.
Simulate migration in a real-world lab setting before deploying new releases in the production network. The test lab can later serve as a classroom for training network personnel.
Prepare temporary backup networks to prevent service interruptions and handle unexpected problems. Deploy releases in stages by following the deployment strategy. First deploy and test releases at the network edge, and then work your way toward the network core.
Operating the Network
The implementation and operation phase overlap. During the implementation phase, new releases are slowly and methodically deployed in the network. During the operation phase, personnel monitor the network as new releases are migrated.
Monitor the network by tracking application or node downtime. Watch for important events, such as EoE announcements or changes in your business, such as an expansion that would require buying new network hardware.
While operating the network, personnel refine processes for its operation and then plan the next migration. Profile the network periodically.
During the implementation phase, track the number of devices that have been migrated to the new releases. Create a migration status report that shows the progress made in migrating to the target releases (see Figure 3).
Monthly Migration Report for August 06
Figure 3. Monthly Migration Report
The monthly migration report shows network equipment and how many devices are running the target releases in actual number and by percentage.
Watch for important business events that affect the network. Purchasing new network hardware or deploying a new application, such as IP telephony, can trigger a new migration cycle. Revisit the planning phase, then review and update the network and business profiles when changes occur. Maintain the migration plan to document all changes made to the network, including installed hardware and software, business objectives, and resources.
The four-phase process is a cycle, not a single event. Repeat the four-phase process at regular intervals, or when major business requirements change. Always replace or add new equipment as part of a four-phase cycle instead of on an impromptu basis. This helps ensure that the network always runs consistent and compatible Cisco IOS Software releases.
Migration Tools
Table 6 describes and lists links to important Cisco IOS Software tools and documentation. You can use the tools to get information about releases, feature sets, platforms, and images. Understanding releases helps you make better decisions when picking a release for migration.
Table 6. Tools and Resources
