Cisco Catalyst switches that run IOS XE, such as the 3650 and 3850 series, support two distinct boot modes: bundle mode and install mode. These modes determine how the switch loads and manages its operating system image and have important implications for software upgrades, system stability, and stack management.
By default, new Catalyst switches ship in install mode. However, many network engineers who are accustomed to older Cisco IOS practices or have maintained devices through manual upgrades may still encounter or use bundle mode. While both modes allow the switch to boot and operate normally, they differ significantly in architecture and operation.
Understanding these differences is critical when upgrading switches, especially in stacked environments where all members must run the same mode to avoid incompatibility. Confusing or mixing the two modes can lead to failed boots, inconsistent software versions across stack members, or prolonged downtime.
This section explores the background and fundamental concepts behind bundle and install modes, highlighting their operational characteristics, advantages, and common use cases. It aims to prepare administrators to manage IOS XE upgrades more effectively and avoid common pitfalls.
What Is Bundle Mode?
Bundle mode represents the legacy method of booting Cisco IOS XE switches. In this mode, the switch boots directly from a single, monolithic IOS XE image file—typically a large .bin file stored in flash memory. The system loads this image fully into RAM during boot and runs the entire operating system from that file.
When using bundle mode, upgrading the IOS XE version involves manually copying the new .bin file to each switch’s flash storage, updating the boot variable to point to the new image, and rebooting the device.
This tells the switch to load the specified bundle file at boot.
Bundle mode is simple and straightforward, especially for standalone switches or small networks. It resembles the traditional IOS behavior familiar to many network engineers. There is no unpacking or extraction involved—the entire image is contained within the .bin file.
However, bundle mode has some notable limitations. Because the switch loads the entire monolithic image into memory, it consumes more RAM during boot compared to install mode. This can affect system performance and boot times, especially on lower-end hardware.
Furthermore, bundle mode disables some advanced IOS XE features, such as auto-upgrade in switch stacks, which automates synchronizing software versions across members. This means upgrades and patching in a stack must be managed manually, increasing operational overhead and the risk of version mismatches.
Because of these constraints, bundle mode is best suited to legacy environments, single switches, or scenarios where manual upgrade control is preferred.
What Is Install Mode?
Install mode is the modern default boot mode for IOS XE Catalyst switches starting with certain software releases and hardware. Instead of booting from a single monolithic .bin file, install mode boots from multiple extracted software packages stored on the device’s flash memory.
These packages have .pkg extensions and represent modular components of the IOS XE operating system, such as the base runtime, routing services, web user interface, and platform drivers. The switch uses a special configuration file called packages.conf to determine which packages to load and in what order.
This modular architecture provides several benefits. Since the switch boots by loading only the necessary packages, it uses less RAM during startup, resulting in faster boot times and improved system responsiveness.
Install mode also supports advanced software management features. For example, the auto-upgrade feature enables seamless upgrades across all members of a switch stack. When a new member is added, it automatically downloads and installs the correct software version, simplifying maintenance and reducing human error.
Administrators do not need to manually copy .bin files to every switch during upgrades. Instead, a single image upgrade command initiates the extraction and installation of the individual packages across the stack.
Because of these advantages, install mode is highly recommended for all new deployments, especially for environments managing multiple switches or switch stacks.
Differences Between Bundle Mode and Install Mode
The differences between bundle and install mode affect both operational procedures and system behavior. Understanding these distinctions helps network engineers make informed decisions and avoid common upgrade pitfalls.
- Image Format
Bundle mode uses a single monolithic .bin image file to boot the switch. Install mode uses multiple extracted .pkg files along with a packages.conf file that instructs the system on package loading. - Memory Usage
Bundle mode loads the entire .bin image into RAM, consuming more memory during boot. Install mode loads only needed packages, leading to lower memory use and faster startup. - Upgrade Process
Bundle mode upgrades require manually copying the .bin image to each device and updating the boot variable. Install mode upgrades use a single command that extracts and installs the image packages automatically, supporting stack-wide upgrades. - Stack Management
Auto-upgrade and synchronization features are only supported in install mode. Bundle mode requires manual synchronization of software versions in stack members, increasing operational complexity. - File System Impact
Install mode keeps .pkg files in flash and manages packages explicitly; the .bin file can be deleted after extraction, saving space. Bundle mode retains the .bin image as the only boot file. - Boot Variables
Bundle mode boot variables point directly to the .bin file. Install mode boot variables refer to the packages.conf file. - Support and Recommendations
New Catalyst switches ship with install mode enabled by default. Cisco recommends using install mode for all new installations and upgrades.
Potential Issues Mixing Modes in Switch Stacks
Switch stacks require all members to run the same boot mode to maintain software and operational compatibility. Mixing install mode and bundle mode devices within the same stack can cause multiple problems:
- Stack members may fail to join or stay in the stack due to software mismatch.
- Inconsistent feature availability may cause erratic behavior.
- Upgrades may fail or cause partial updates leading to downtime.
- Troubleshooting becomes more complex due to mode differences.
When managing a switch stack, always verify the boot mode of all members before performing software upgrades or adding new devices.
The command show version reveals the current boot mode by displaying whether the switch uses packages.conf (install mode) or boots directly from a .bin file (bundle mode).
In summary, IOS XE Catalyst switches support two modes for booting and image management: bundle mode and install mode. Bundle mode is simpler and uses a monolithic image but is limited in automation and efficiency. Install mode is modular, memory-efficient, supports automated upgrades and stack synchronization, and is the recommended default for modern deployments.
Understanding these modes helps network engineers plan upgrades correctly, manage stacks safely, and avoid downtime due to mode mismatches. Moving forward, organizations are encouraged to adopt install mode for easier operations and better scalability.
Detailed Operation of Install Mode on IOS XE Switches
Install Mode is the default and recommended boot mode for modern IOS XE Catalyst switches. Unlike Bundle Mode, which uses a monolithic image, Install Mode boots the switch using multiple modular software packages extracted from a single bundle image. This modularity improves efficiency, scalability, and manageability, especially in large networks and switch stacks.
When a switch is running in Install Mode, the software image on flash is not a single executable .bin file but rather a collection of .pkg files. These packages each contain different components of the operating system — such as the base operating system, routing modules, drivers, web user interface, and additional features.
A critical file named packages.conf orchestrates the loading of these packages during boot. It acts as a manifest, instructing the switch on which packages to load and their sequence. This file is generated automatically during image extraction and should never be manually edited.
Image Extraction and Package Management
To enter Install Mode, the switch extracts the .pkg files from the downloaded .bin image during installation. The .bin file acts as a compressed archive containing all necessary packages.
This extraction process is automated when using platform-specific software installation commands. Instead of manually copying images and setting boot variables, administrators issue a single command which handles unpacking, installing, and configuring the software correctly.
The extracted .pkg files consume more flash space initially than the single .bin file, but since Install Mode operates on these packages directly, it reduces memory consumption and boot times.
Administrators can clean up unused or older package files after an upgrade to reclaim disk space, but this should be done with care because the removed packages cannot be used for rollbacks.
Upgrading Switches Using Install Mode Commands
Software upgrades in Install Mode leverage specific commands that simplify the upgrade and minimize operational risks. These commands vary slightly depending on the IOS XE version.
This will initiate the upgrade for all switches in the stack, automatically copying and installing the packages on each member. It handles coordination, package extraction, and boot variable configuration internally.
For older versions (pre-Denali), a similar command called software install is used, but it lacks the auto-copy feature.
The key benefit here is that with Install Mode, the switch stack does not require manual copying of the image to each member’s flash. The command distributes the image automatically, reducing errors and administrative overhead.
Auto-Upgrade Feature in Install Mode
One of the most compelling reasons to use Install Mode in switch stacks is the support for auto-upgrade. This feature ensures consistency when adding new members to a stack or upgrading existing ones.
The active switch in the stack will detect if a new member is running a different software version. If so, it will automatically push the correct IOS XE packages to the new switch, install them, and bring it into the stack with the same software version as other members.
This capability simplifies operations and reduces downtime during expansion or maintenance. It also prevents issues caused by version mismatches within the stack, a common problem in Bundle Mode deployments.
Disk Space Considerations and Cleanup Commands
Because Install Mode stores multiple .pkg files, disk space management becomes important, especially on devices with limited flash capacity.
Old packages from previous upgrades accumulate unless explicitly cleaned. This will delete all software packages that are not currently active and removes files used for rollback purposes. Use this command cautiously because once removed, rollback to previous software versions requires re-uploading packages.
Additionally, the original .bin image file can be deleted after installation since the switch boots from the extracted .pkg files. This can reclaim substantial flash space without impacting operation.
Careful planning of disk space and cleanup scheduling helps maintain switch health and prevents issues related to full flash during future upgrades.
Restrictions and Limitations in Install Mode
Despite its benefits, Install Mode has a few restrictions administrators should be aware of:
- Booting the switch from USB drives or TFTP is not supported in Install Mode. The switch must boot from packages stored on the internal flash memory.
- All switches in a stack must share the same licensing to run in Install Mode. License mismatches can cause stack or feature inconsistencies.
- Certain legacy management features or older tools may not fully support Install Mode, requiring updated workflows or scripts.
Understanding these limitations ensures that operational plans and maintenance procedures are aligned with the capabilities of Install Mode.
Summary of Install Mode Benefits
Install Mode offers numerous advantages over Bundle Mode:
- Reduced RAM usage and faster boot times by loading modular packages rather than a full image.
- Simplified and automated software upgrades, especially in switch stacks.
- Support for auto-upgrade, enabling new stack members to be provisioned quickly and consistently.
- Cleaner flash storage management through extracted packages and optional cleanup commands.
- Better alignment with Cisco’s future IOS XE development direction, as Install Mode is the preferred default.
For modern network environments aiming for scalability, automation, and efficient management, Install Mode provides clear operational benefits that reduce downtime and simplify life for network administrators.
Understanding Bundle Mode on IOS XE Catalyst Switches
Bundle mode is the traditional and simpler boot method used by Cisco IOS XE Catalyst switches, including models like the 3650 and 3850 series. In this mode, the switch boots directly from a single monolithic image file stored on the device’s flash memory. This image is typically a large .bin file, which contains the entire operating system and feature set required by the switch.
When the switch is powered on or rebooted, it loads this .bin image into RAM and executes the software from there. Because the entire IOS XE system is packaged into this one file, bundle mode resembles the classic IOS boot process familiar to many network administrators who have managed Cisco devices for years.
While bundle mode’s simplicity can be attractive, especially for small deployments or standalone switches, it also brings certain drawbacks and operational limitations that should be carefully considered.
How Bundle Mode Works in Practice
This .bin file is stored in the switch’s flash memory. The switch’s boot loader reads this file and loads it into RAM during startup. Because it is a single large file, the entire contents of the image must fit in the device’s memory.
The network administrator sets the boot variable manually to point to the desired .bin image file.
After configuring the boot variable, a reload is necessary to make the switch boot from the newly specified image.
Since this boot mode treats the entire .bin image as one unit, there is no modular unpacking or extraction of separate software packages. The switch only manages the .bin file and executes it as a whole.
Upgrade Process Using Bundle Mode
Upgrading a switch running in bundle mode involves several manual steps:
- Download the new IOS XE image — The administrator downloads the desired .bin image file from Cisco’s software repository or another trusted source.
- Transfer the image to the switch flash — Using methods like TFTP, FTP, or USB, the .bin file is copied to the switch’s flash memory. Each switch must receive the new image individually.
- Set the boot system variable — The administrator updates the boot variable to point to the new image file, as shown in the previous section.
- Save the configuration — To make the boot variable persistent across reloads.
- Reload the switch — The switch reboots and loads the new image.
This upgrade process is repeated for each switch in the network or switch stack.
While this approach is straightforward, it becomes inefficient and error-prone in multi-switch environments or stacks. Each switch must be manually updated, and if any switch runs a different image version or mode, the stack may become unstable.
Limitations and Challenges of Bundle Mode
Although bundle mode is conceptually simpler, it has several important limitations:
Increased Memory Usage and Boot Times
Loading a large monolithic .bin image file requires substantial RAM during boot. On switches with limited memory resources, this can lead to increased boot times and reduced memory available for runtime processes.
In contrast, Install mode extracts and loads only the necessary packages, reducing RAM footprint and improving boot speed.
Lack of Automation in Stack Upgrades
Bundle mode does not support the auto-upgrade feature available in Install mode. In a switch stack, this means administrators must manually upgrade each member’s image and verify version consistency.
Manual upgrades increase the risk of human error, misconfiguration, or version mismatches that can cause stack failures or degraded performance.
No Modular Software Updates
Bundle mode requires downloading and installing the entire IOS XE image for any upgrade or patch. Even minor fixes require transferring the full .bin image.
Install mode supports modular package upgrades, allowing administrators to update or patch individual components without a full image reinstall, saving time and bandwidth.
No Support for Auto-Copy or Centralized Image Management
Bundle mode lacks the capability to automatically distribute images to new stack members. When adding switches to an existing stack, administrators must manually copy and configure the image on the new switch.
This increases the complexity of stack expansions and lengthens deployment timelines.
Limited Compatibility
Cisco’s roadmap favors Install mode as the preferred boot method for IOS XE devices. Many new features and enhancements are designed with Install mode in mind. Using bundle mode may limit access to future functionality or require eventual migration.
Identifying Bundle Mode on a Switch
The output will include information about the running image. If the switch is in bundle mode, it will show a boot variable pointing directly to a .bin file and no mention of extracted packages or packages.conf.
This indicates the switch boots from the monolithic bundle image.
In contrast, Install mode references the packages.conf file and extracted .pkg files.
Best Practices for Managing Bundle Mode Switches
If you operate switches in bundle mode, observe the following best practices to maintain stability and reduce errors:
- Always verify that all stack members run the same image version and boot mode before forming or expanding a stack.
- Use consistent naming conventions for .bin files to avoid confusion during upgrades.
- Carefully plan upgrades during maintenance windows to minimize downtime.
- Test upgrades on standalone devices before deploying across stacks.
- Maintain detailed records of image versions and boot variable settings.
- When possible, evaluate migrating to Install mode to benefit from automation and modular upgrades.
Migration Considerations: Moving from Bundle Mode to Install Mode
Organizations running bundle mode switches may consider migrating to install mode to leverage its advantages.
Migration involves extracting the monolithic .bin image into the modular .pkg format, creating a valid packages.conf, and configuring the boot process to use this package provisioning.
Cisco provides tools and documented procedures for this migration, which should be followed carefully to avoid device downtime or boot failures.
Key steps include:
- Using platform-specific install commands to perform the extraction and package installation.
- Verifying successful boot in install mode before removing the bundle mode .bin file.
- Ensuring all stack members are converted consistently.
Migration requires planning, testing, and validation but can result in improved manageability and stability.
Bundle mode offers a simple and traditional way to boot Cisco IOS XE Catalyst switches from a single monolithic .bin image file. While functional and familiar, it has limitations regarding memory usage, stack management, upgrade automation, and future feature support.
Bundle mode upgrades are manual and require careful coordination, especially in stacked environments. It is essential to maintain consistent boot modes across all stack members to avoid compatibility issues.
For modern networks, install mode is preferred due to its modular architecture, reduced resource demands, and support for auto-upgrade features. However, bundle mode remains in use in many existing deployments, and understanding its operation is critical for effective network management.
Administrators should carefully evaluate their network environment, operational needs, and future growth plans when deciding between bundle and install modes. Proper planning, mode verification, and upgrade procedures help ensure stable, efficient switch operation.
Troubleshooting Common Issues in Bundle and Install Modes
When managing Cisco IOS XE Catalyst switches, understanding how to troubleshoot problems related to bundle and install modes is essential. Both modes have unique characteristics that can lead to different issues if not managed properly.
Boot Failures and Mode Mismatches
One of the most common issues occurs when switches in a stack run different boot modes. Since stack members must operate in the same mode, mixing bundle and install mode switches can cause the stack to fail to form or lose synchronization.
Symptoms include:
- Stack members stuck in “standalone” mode
- Failure to elect a master switch
- Stack members dropping out or rebooting unexpectedly
To troubleshoot this, verify the mode on each switch using show version. If a mismatch is found, consider migrating all members to the same mode before attempting stack formation.
Image Corruption and Flash Space Issues
Improper copying of IOS images can lead to corrupt files on flash, causing boot failures or unexpected reloads.
In bundle mode, since the switch boots from a single .bin file, corruption affects the entire image.
In install mode, corruption in any .pkg file or the packages.conf file can prevent successful boot.
Verify file sizes and dates. Use verify commands if available, and consider re-copying the image if corruption is suspected.
To free unused package files after confirming the current image is stable.
Software Upgrade Failures
Upgrades may fail due to syntax errors in commands, insufficient disk space, or unsupported operations (e.g., trying to boot from USB in install mode).
Carefully review IOS XE version requirements and use the appropriate installation commands for your software version:
Monitor upgrade progress and review logs for errors.
Configuration and Licensing Issues
In install mode, all switches in a stack must have compatible licenses. Licensing mismatches can cause features to be disabled or switches to operate incorrectly.
Ensure all stack members have consistent licenses and feature sets before upgrading or adding switches.
Best Practices for Managing IOS XE Boot Modes
To ensure reliable operations and simplified management, adhere to the following best practices.
Consistent Boot Mode Across Switch Stacks
Always ensure all members of a stack run the same boot mode—preferably install mode for modern deployments. Use show version regularly to audit switch mode and prevent mismatches.
Use Install Mode for New Deployments
Given its advantages in memory usage, upgrade automation, and scalability, install mode is recommended for all new installations and upgrades.
Use Platform-Specific Installation Commands
Always use Cisco’s documented install commands appropriate for your IOS XE version. Avoid manual copying of images or direct edits to packages.conf or package files.
Clean Up Unused Packages Periodically
Free flash space by removing unused .pkg files after upgrades using:
Request platform software package, clean switch all file flash:
Be aware this will delete rollback files and should be done only after confirming stable operation.
Enable Auto-Upgrade in Switch Stacks
Enable the auto-upgrade feature to simplify adding new members and managing upgrades.
This reduces operational overhead and minimizes stack version mismatches.
Backup Configuration and Images Before Upgrades
Before performing software upgrades, backup switch configurations and current images to avoid data loss in case of failure.
Migrating Between Bundle and Install Modes
Migration between modes is sometimes necessary due to operational requirements or to take advantage of newer features.
Converting Bundle Mode to Install Mode
Converting requires extracting the .bin image into .pkg packages and configuring the boot to use packages.conf.
Verify successful boot into install mode and consistent operation before removing the bundle image.
Converting Install Mode to Bundle Mode
This is less common and generally not recommended but can be done by setting the boot variable to the .bin file and rebooting.
Be cautious as this disables stack auto-upgrade and requires manual management of images.
Operational Tips for Large Deployments
In large networks, managing IOS XE modes at scale requires planning.
- Standardize on Install Mode: Define install mode as the baseline for all new devices.
- Use Automated Tools: Integrate upgrade commands into automation frameworks for consistency.
- Document Mode and Version: Keep detailed inventory records including boot mode and software version.
- Monitor Flash Usage: Proactively monitor flash storage and perform cleanup regularly.
- Train Staff: Ensure network engineers understand differences and commands for both modes.
The choice between bundle and install mode impacts IOS XE Catalyst switch operations significantly. While bundle mode offers a familiar and straightforward approach, install mode provides improved memory efficiency, automation, and scalability.
By understanding their differences, limitations, and operational nuances, administrators can reduce upgrade complexity, prevent stack issues, and streamline network management.
Following best practices around mode consistency, upgrade procedures, and cleanup ensures network stability and prepares organizations for future IOS XE advancements.
Final Thoughts
Choosing the right boot mode for IOS XE Catalyst switches is a crucial decision that affects upgrade processes, system stability, and overall network management. While bundle mode offers a straightforward, legacy-style approach—booting from a single monolithic image—it has limitations in memory use, automation, and scalability, especially in switch stacks.
Install mode, the default for newer switches, leverages a modular, package-based architecture that reduces memory consumption, enables faster boots, and supports automated upgrades across stack members. This mode aligns with Cisco’s long-term IOS XE development and simplifies operations for modern network environments.
Network administrators should always verify the current boot mode on their devices before upgrading or adding switches to a stack. Mixing modes within a stack is unsupported and leads to instability and complex troubleshooting.
When possible, migrating to install mode is advisable to take advantage of its operational benefits, including auto-upgrade features that save time and reduce human error. However, migration requires careful planning and adherence to Cisco’s recommended procedures.
Effective management of flash space, software licensing, and upgrade commands ensures smooth, predictable switch behavior. Regular housekeeping such as cleaning up unused packages helps maintain device health and frees resources for new software versions.
In large or growing networks, standardizing on install mode, documenting switch modes and versions, and leveraging automation tools for upgrades can greatly improve efficiency and reduce downtime.
Ultimately, understanding the differences between bundle and install modes equips network engineers with the knowledge to maintain stable, scalable Catalyst switch deployments and respond confidently to evolving operational needs.