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Cisco Catalyst 9300 1:1 Redundancy Overview

Today I am going to talk about the 1:1 Redundancy in Cisco Catalyst 9300 switch. Cisco Catalyst 9300 is one of the most adopted switch model in the access layer and is one of the replacement of Cisco 3850 or 3650 in next couple of years.

Cisco 9300 comes up with the 24/48 port switch with POE, POE+ or UPOE models. The need of POE is very essential when you are going to deploy the IOT based devices in your network and Cisco comes up with the Cisco 9300 switch with more and more POE based switches.

Let's talk about the 1:1 Redundancy in Cisco 9300 catalyst Switches.

What Cisco says about the 1:1 Redundancy, It is used to assign active and standby roles to specific switches in the stack of Cisco 9300 stacks. This overrides the traditional N+1 role selection algorithm, where any switch in the stack can be active or standby. 

Fig 1.1- Switch Stacking
In 1:1 redundancy, the stack manager determines the active and standby role for a specific switch, based on the flash rommon variable. 

The algorithm assigns one switch as active, another switch as standby, and rest of the switches will all be members. Whenever an active switch reboots it becomes standby and the existing standby switch will become active. The existing member switches will all be in the same state. This feature was introduced in 16.6.1.

RouteXP_Switch#switch 1 role active
RouteXP_Switch-9300-1#switch 1 role active 
WARNING: Changing the switch priority may result in a configuration change for that switch. Do you want to continue?[y/n]? [yes]: 

RouteXP_Switch-9300-2# switch 2 role standby


Clearing Roles
RouteXP_Switch-9300-1#switch clear stack-mode 
WARNING: Changing the switch priority may result in a configuration change for that switch. Do you want to continue?[y/n]? [yes]:

Will the members of a stack take over in 1:1 Redundancy mode if the active and standby go down?
No. In fact, the members will reload. Upon reload the members will boot loop. After 5 reloads it will go into rommon

Waiting for 120 seconds for other switches to boot
#################################################################################
Switch number is 3

Chassis 3 reloading, reason - Active/standby selection failed in 1+1 Model
Switch rebooted continuously for at-least 5 times. Disabling auto-reboot
Jun 10 11:23:3

Initializing Hardware...

System Bootstrap, Version 16.6.1r [FC1], RELEASE SOFTWARE (P)
Compiled Sat 07/15/2017 8:31:57.39 by rel
Current image running: 
Primary Rommon Image
Last reset cause: SoftwareReload
C9300-24U platform with 8388608 Kbytes of main memory
switch: 

If the active goes down and comes back up, do we preempt? Aka switch old-active back to active role?
The answer is No.
RouteXP_Switch-9300-1#sh switch stack-mode 
Switch#  Role    Mac Address     Version   Mode  Configured  State 
--------------------------------------------------------------------------------------------------------------------
 1      Member   706b.b929.f700    V01     1+1     Active     Ready               
*2      Active   cc98.911a.0500    V01     1+1     Standby    Ready               
 3      Member   cc98.911a.c380    V01     1+1     Member     Ready               


RouteXP_Switch-9300-1#
*Jun 10 11:39:38.046: %STACKMGR-6-STANDBY_ELECTED: Switch 2 R0/0: stack_mgr:  Switch 1 has been elected STANDBY. 
*Jun 10 19 11:39:38.047: %IOSXE_REDUNDANCY-6-PEER: Active detected switch 1 as standby.
*Jun 10 11:40:03.060: %REDUNDANCY-5-PEER_MONITOR_EVENT: Active detected a standby insertion (raw-event=PEER_FOUND(4))

*Jun 10 11:40:03.060: %REDUNDANCY-5-PEER_MONITOR_EVENT: Active detected a standby insertion (raw-event=PEER_REDUNDANCY_STATE_CHANG
*Jun 10 11:40:43.060: %HA_CONFIG_SYNC-6-BULK_CFGSYNC_SUCCEED: Bulk Sync succeeded
*Jun 10 11:40:53.060: %RF-5-RF_TERMINAL_STATE: Terminal state reached for (SSO)

RouteXP_Switch-9300-1#sh switch stack-mode 
Switch# Role Mac Address Version Mode Configured State 
--------------------------------------------------------------------------------------------------------------------
 1 Standby 706b.b929.f700 V01 1+1 Active Ready 
*2 Active cc98.911a.0500 V01 1+1 Standby Ready 
 3 Member cc98.911a.c380 V01 1+1 Member Ready 


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