How to Write a network cutover Solution

Since I was engaged in O & M work, many network cutover operations have been performed many times. Most cutover operations are performed at in the evening, so the dark-Night Eye appears, "the eyes of the dark night, the unbounded network connection, and the world of IT people ", I believe that the majority of O & M peers also feel this.

Network cutover is also called network migration. It refers to physical or logical changes to the running network. Because the network cutover is to operate on the lines and devices in use, it will directly affect the services carried above, if a cutover error occurs, the service application may be interrupted or even cause unnecessary economic losses. Therefore, a detailed cutover scheme must be formulated.

How can we develop a detailed and complete cutover scheme? Next I will talk about how to write a standardized and meticulous cutover Document Based on my personal experience.
1. Describe the project background

Generally, the cutover plan you wrote needs to be reported to the superior, and the relevant leaders do not necessarily understand the project. Therefore, you need to describe the project background and briefly introduce the project.

Ii. Formulate overall cutover scheme and Plan

Many network cutovers are not completed in one step. They are usually divided into multiple small cutovers. At this time, a general cutover scheme and a combination of many specific cutover schemes are required to describe the entire process.
The cutover scheme not only describes the tasks that need to be performed in the cutover, but also contains the task schedules. Therefore, the relevant content should be discussed and approved by various cooperation departments and units.

Iii. Compile specific cutover Implementation Scheme

1. Preparations before cutover

Prior to cutover, you need to make careful preparations. You should not only send an email to the responsible party or the responsible person, but also call to confirm. Once I made a cutover, I only sent an email to the partner without making a phone call to confirm the result. When the cutover was completed, no one from the other and sent someone urgently, which delayed a lot of time. In addition, the specific cutover steps involved in cutover should not only be discussed on paper, especially the large changes involving software versions or system updates and upgrades. Generally, a simulated environment should be set up to perform a simulated cutover test. Any hasty launch without tests may have disastrous consequences. I remember that when I was doing security integrated cutover, a buddy ignored the relationship between a default route and the introduction of OSPF static routes, and almost caused a Network Fault Caused by the self-loop routing. Generally, the Business Operation Network must be uninterrupted for 24 hours. If the business is interrupted for several hours after a large-scale upgrade, it will be miserable. Therefore, the simulation test before cutover is a rigorous step to verify the feasibility of the cutover scheme. Strict tests help to reduce the risks in this regard, and this preparation work cannot be ignored by everyone.
Preparations before cutover include notifying relevant departments and customers, confirming contacts, preparing cutover materials, backing up data, and collecting information.
 

2. cutover networking diagram:

The network topology of related partners and the connection diagram of upstream and downstream devices, including their device models, ports, and relevant parameters, should be clarified to facilitate the preparation of network commands and keep them for future reference.

The following shows an example of network topology and device interconnection parameters:
 

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3. Description of the scope and risks of cutover online:

Clearly define the scope. In short, You Need To Know What goals are achieved and what businesses are launched, and do not go beyond the scope specified in advance. If there are large discrepancies, stop cutover and re-develop a cutover scheme to prevent major accidents. In addition, cutover may also fail. In this case, there should be an emergency plan or a rollback plan.

4. cutover organization and personnel arrangement: A cutover group is established by the superior leadership to determine the cutover owner, the contact owner, the manufacturer owner, and the construction owner. A clear division of labor is also written.

5. Formal cutover steps and procedures:
In the formal cutover scheme, the cutover content of each step needs to be detailed, the plan should include the start time, end time, last rollback time, and the impact of the step on each business.

Notes during actual operations:
A. take A snapshot before each step: several minutes before this step, record the status, traffic, and Protocol of the existing port on the operating device, and back up the configuration file of the device.
B. cutover: Execute the cutover command or related operations.
C. check whether it is successful: run the show/display/ping/traceroute command to check whether it is successful. If conditions are met, you can verify it from the client.

6. rollback steps: If the cutover fails, the status before cutover should be restored. Generally, if an exception or failure occurs in the middle and cannot be recovered within the specified time, the system should be rolled back.

Note: In the cutover process, you must strictly follow the cutover steps. You cannot perform the next step before the previous step is confirmed. The relevant personnel and implementers who participate in the cutover should take every detail of the work seriously, strengthen mutual collaboration and timely communication to ensure smooth cutover.

Iv. Test After cutover is completed

After the cutover is completed, an overall test should also be conducted. This complete test includes not only the device layer, but also the application layer test and traffic flow observation.

 

5. Observation on duty after cutover

 
After cutover, relevant technical personnel should be arranged to be on duty or on-call duty, and problems should be reported and resolved in a timely manner. Arrange operators to inspect the business and various functions. Generally, if the service is normal within 24 hours, the cutover is completed successfully.

Conclusion: after a complete cutover scheme is developed and fully prepared, the cutover work will be easier. The implementers only need to strictly follow the scheme.

Outline of cutover documentation:

1. Project Background
Ii. Overall cutover scheme and Plan
Iii. Specific cutover Implementation Plan
1. Preparations before cutover
2. cutover networking Diagram
3. Scope and risks of cutover online
4. cutover organization and personnel arrangement
5. Formal cutover steps and procedures
6. rollback steps
Iv. Test After cutover is completed
5. Observation on duty after cutover

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