I have MX480 with two Routing engine (re0,re1). By default, re0 is a master, re1 is a backup. I've update re1 with version 18.1R2.5, then made re1 as a master ( request chassis routing-engine master switch). But re0, I couldn't update, I created case, Juniper send me new routing engine. So, my question is: When I pull it back to the MX480 in slot0 what would happened ? re1 still be the master or re0 will become the master.
By default, Junos OS uses re0 as the master Routing Engine and re1 as the backup Routing Engine. Unless otherwise specified in the configuration.
could you share the following output from router:
> show configuration chassis
Routing Engine status: Slot 1: Current state Master Election priority Backup Temperature 30 degrees C / 86 degrees F CPU temperature 38 degrees C / 100 degrees F DRAM 3584 MB (4096 MB installed) Memory utilization 10 percent 5 sec CPU utilization: User 1 percent Background 0 percent Kernel 4 percent Interrupt 0 percent Idle 95 percent 1 min CPU utilization: User 1 percent Background 0 percent Kernel 4 percent Interrupt 0 percent Idle 94 percent 5 min CPU utilization: User 1 percent Background 0 percent Kernel 4 percent Interrupt 0 percent Idle 94 percent 15 min CPU utilization: User 1 percent Background 0 percent Kernel 4 percent Interrupt 0 percent Idle 95 percent Model RE-S-2000 Serial ID 9012022222 Start time 2018-07-01 02:19:26 ALMT Uptime 86 days, 12 hours, 57 minutes, 35 seconds Last reboot reason Router rebooted after a normal shutdown. Load averages: 1 minute 5 minute 15 minute 0.62 0.74 0.70
From the below o/p, there no "(default)" next to "current state" which means you have configured RE0 to be master and RE1 under the "set chassis redundancy routing-engine <0/1> <master/backup>" stanza.
Routing Engine status: Slot 1: Current state Master Election priority Backup
So you in your case, after the backup Routing Engine takes mastership, it continues to function as master even after the originally configured master Routing Engine has successfully resumed operation (that is when you insert new RE in slot-0). You must manually restore it to its previous backup status. (However, if at any time one of the Routing Engines is not present, the other Routing Engine becomes master automatically, regardless of how redundancy is configured.)