Here's how to upgrade SONiC in a VLT environment, using USB drives. You’ll need two drives formatted as FAT32, the SONiC image, and physical access to your switches. Download the image from your Dell My Account. For more information see KB Article 180674. This is not a comprehensive guide. Before attempting an upgrade please read the 'SONiC Installation and Upgrade Guide' carefully.
In particular, check the 'Configuration Migration Support' section to confirm upgrade compatibility. Before upgrading SONiC, first upgrade the ONIE Software, then the Networking Firmware. These are available on Dell.com/Support. Please remember there is always a risk of traffic loss during a VLT upgrade. We recommend scheduling a maintenance window to do this. Insert a FAT32 drive with the SONiC image in the root directory, in each switch Connect to each VLT peer using a terminal emulator, here we're using PuTTY. Once connected run 'sonic-cli' to enter the Management Framework CLI.
To enable your USB drives, run 'configure terminal', 'usb enable' then 'exit'. Run 'dir usb' and confirm your SONiC image is available. Before proceeding, save and backup your switch configurations. On each peer, run 'write memory' to save the running configuration to the startup configuration.
Then use the 'copy startup-configuration' command to backup the config to your USB drives. Optionally, as an extra precaution, run 'show running-configuration | no-more', copy the output, and paste it into a text file on your workstation. Use the 'copy' command to transfer your image to each switch. Then 'image install' to begin the installation Run 'show image status' to check the progress. It usually only takes a minute or two to complete. Upgrade the standby VLT peer first to minimize traffic disruption Run 'show mclag brief' to see which peer is standby. Here, at the moment, it's S5248F-2. Also confirm both 'Session Status' and 'Peer Link Status' are 'Up'. On the standby peer only, run 'show image list' to check that 'next:' displays the correct image.
Then, run 'reboot' to reboot the switch. When the reboot is complete, and 'System is ready' is displayed, log back into the switch, and run 'sonic-cli'. Run 'show mclag brief' and again confirm both 'Session Status' and 'Peer Link Status' are 'Up'. Then 'show version' to confirm the OS version is correct. Now repeat the same steps on your other peer. Run 'show image list' to check that 'next:' displays the correct image. Run 'show mclag brief' and confirm both 'Session Status' and 'Peer Link Status' are 'Up'.
If they are, run 'reboot' to reboot the switch. When complete, log back in and run 'sonic-cli'. Again, run 'show mclag brief' and confirm both 'Session Status' and 'Peer Link Status' are 'Up'. Then 'show version' to confirm the OS version is correct. The OS upgrade is now complete. If you made any other changes, remember to save your configuration with 'write memory' before quitting. Thanks for watching.
