Keeping DHCP DB after upgading switches in VSS

[mitros]

Hello,

I have two C9407 in VSS (being DHCP server too). I want to upgrade their iOS from 16.9.2 to 17.12.3, so ISSU is not an option. What is the best way to do this and keep DHCP leases ?

Best regards

TIA

[MHM Cisco World]

I have idea and make search and find that indeed it can solution here 
https://networkengineering.stackexchange.com/questions/41468/reserve-an-ip-for-client-on-cisco-dhcp-server

copy the dhcp database into tftp and then restore it back after upgrade 
MHM

[Reza Sharifi]

Hi,

The DHCP lease is part of the running config, and as long as the config is saved, upgrading the IOS should not affect it.

Since ISSUE is not supported, load the new IOS in both chassis, change the boot parameter to reflect the new IOS, save the config, and reboot both chassis in a maintenance window.

HTH

[Leo Laohoo]

I call this process the NSFW + One-Hit-Wonder (or One-Hit-Wonder for short).

Read (and understand) the steps carefully because everything in this process is meant to allow the operator to confirm that the switch (or VSS pair) will boot the intended version.

Any questions, ask.

[mitros]

Thanks a lot.

@Leo Laohoo As I understood, new image should be copied on active switch only (to "bootflash:") and later only rename proper ".conf" file both on "bootflash:" and "bootflash-2-0:" ?