ME3400 doesn't support ISSU. Depending on where is the switch you may have a backup path available which would allow you to make the upgrade without disrupting the service.
Thanks for your reply, Laurent.
Do you have any document which provides you detailed procedure to how to upgrade ME3400, i have hundreds of ME3400 which need upgrade.
Can i do chunks of ME3400 simaltanously. i need a solution for this task, its really critical for me because most of the ME3400 has no any backup links because it is most cutomer facing UPE'S for our MPLS Cloud.
Looking forward to hear soon.
Here is a link which describe the upgrade procedure: https://www.cisco.com/en/US/docs/switches/metro/me3400e/software/release/12.2_53_se/release/notes/OL21150.html#wp559616
You could upload the new version to all the switches during the day and do the reload during a maintenance window. I don't recommend rebooting all the switches at the same time.
Also Cisco Works if you are using it allows you to upgrade several devices at the same time.
after having followed the SW procedure suggested by Laurent you can use
reload at ?
hh:mm Time to reload (hh:mm)
to schedule reload at a different time on each switch
as noted by Laurent you can take advantage of cisco works to schedule a job with reload command
Hope to help