Catalyst 9800 Failover Behavior

[GHOZLANE Haroun]

In a Cisco  Catalyst Controller 9800 SSO deployment, will failover occur if the interface or port-channel of the active WLC is physically shut down?

[MHM Cisco World]

You use RMI ?

if Yes then 
if PO to SW is shut in active the standby failover to be new active 

MHM

[GHOZLANE Haroun]

It's not working for me—failover only occurs when the active WLC goes completely down.

Our deployment has the WLCs in VSS Pair mode without any split links or cross cables. Could this configuration affect failover behavior?

[MHM Cisco World]

I mention RMI' do you use it?

MHM

[MHM Cisco World]

if you use RMI and it down then your case is third in table 

MHM

[GHOZLANE Haroun]

i am using layer two porchannel as bellow

In my  failover test, I shut down the port channel from the switch side. As a result, the access points and clients disconnected and did not switch over to the backup wlc02.

This behavior suggests that the redundancy mechanisms did not function as expected.

!
interface Vlan100
description Wireless Management
ip address 10.160.1.5 255.255.255.0 secondary
ip address 10.160.1.7 255.255.255.0
!

!
interface Port-channel10
description ###to-WLC-DCO1###
switchport trunk allowed vlan 100
switchport mode trunk
end

DC01-WLC01#sh etherchannel 10 summary
Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
U - in use f - failed to allocate aggregator

M - not in use, minimum links not met
u - unsuitable for bundling
w - waiting to be aggregated
d - default port

A - formed by Auto LAG

Number of channel-groups in use: 1
Number of aggregators: 1

Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
10 Po10(SU) LACP Te0/1/0(P) Te0/1/1(P)

[Mark Elsen]

 - @GHOZLANE Haroun >...In my  failover test, I shut down the port channel from the switch side. As a result, the access points and clients disconnected and did not switch over to the backup wlc02.

   - The phrasing and test sequence is incorrect , controller failover targets inner health checks and operations of the controllers and does not include external networking issues. A real controller failover can make APs switchover , which is transparent in HA SSO.

 M.

[MHM Cisco World]

As @Mark Elsen  mentioned' you need to shut down PO from SW to test .

Why? If you shutdown the PO from active WLC itself the config is sync to standby abd hence now both WLC have PO down and this is case 4 in table which is dont force failover 

MHM

[GHOZLANE Haroun]

yes it is configured ,

!
interface Vlan100
description Wireless Management
ip address 10.160.1.5 255.255.255.0 secondary
ip address 10.160.1.7 255.255.255.0
!

[Flavio Miranda]

@GHOZLANE Haroun 

 It should failover as long as the Active WLC is using this port-channel to reach its gateway. And the RD port is communicating through your VSS switch.

[Leo Laohoo]

Yes and no. 

In theory, yes. 

In reality, it will depend on multiple factors, such as: 

1.  Are the controllers 9800-L or the bigger units (multiple WNCD);

2.  In multi- or single WNCD, depends on the uptime

3.  In single- or multi-WNCD, depends on the code

4.  In multi-WNCD, depends on the control-plane memory utilization

5.  In multi-WNCD, depends on the AP count, daily wireless users, is the SSID PSK or not, etc

[Rich R]

Make sure you refer to the later (17.6) version of the doc you quoted:
https://www.cisco.com/c/dam/en/us/td/docs/wireless/controller/9800/17-6/deployment-guide/c9800-ha-sso-deployment-guide-rel-17-6.pdf
As there were a number of enhancements to SSO between 17.1 and 17.6.

Also see https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/technical-reference/c9800-best-practices.html#StatefulswitchoverSSO and https://www.ciscolive.com/c/dam/r/ciscolive/apjc/docs/2023/pdf/BRKEWN-2846.pdf
It's recommended to have the RP link connected back to back if at all possible and not through the switch network as it seems you're doing.

What version of software are you running? (refer to TAC recommended link below)