Cisco 4500X VSS port-channel issue after upgrading

[PECET]

Hello Everyone,

I am currently encountering an issue after upgrading 2 4500X in VSS. One of the switches has boot in Rommon. After a lot of reloading, booting in Rommon, and unable to establish VSS again, I've decided to convert them back to standalone mode using the switch convert mode stand-alone command. 

Now that they have been both upgraded to 3.11.3aE, I've followed the steps here - https://community.cisco.com/t5/networking-documents/virtual-switching-system-vss-configuration-for-cisco-4500-series/ta-p/3147865#toc-hId--764944615 for the VSS configuration. After issuing the switch convert mode virtual​ command, they have reloaded but were unable to establish VSS. I've also noticed that the port-channels' status are DOWN but the port interfaces are UP. I've converted them back again to standalone mode for now in order to troubleshoot the DOWN status of the port-channels. Nothing was touched or changed. Also checked the SFPs and fiber cable so I don't know why the port-channels are DOWN.

Am I missing anything or encountering a bug? I am hoping for any suggestions at this point. Thank you in advance everyone.

Here are snippets of configuration from the standalone mode switches:

Switch 1:

switch virtual domain 100

                                         <-- I don't know why switch 1 command is not appearing here
mac-address use-virtual

!
interface Port-channel10
switchport
switchport mode trunk
switchport nonegotiate
switch virtual link 1
!

interface TenGigabitEthernet1/1
switchport mode trunk
switchport nonegotiate
no cdp enable
no lldp transmit
no lldp receive
channel-group 10 mode on
service-policy output VSL-Queuing-Policy
!

Switch 2:

switch virtual domain 100
switch 2 priority 110
mac-address use-virtual
!

interface Port-channel20
switchport
switchport mode trunk
switchport nonegotiate
switch virtual link 2
!

interface TenGigabitEthernet1/1
switchport mode trunk
switchport nonegotiate
no cdp enable
no lldp transmit
no lldp receive
channel-group 20 mode on
service-policy output VSL-Queuing-Policy
!

[Leo Laohoo]

Did you upgrade the ROMMON?

In the Release Notes, it is stated:

If you are upgrading to Cisco IOS XE Release 3.9.xE and plan to use VSS, you must upgrade your ROMMON to IOS Version 15.0(1r)SG11.

[PECET]

Hi, our ROMMON version is 15.0(1r)SG12. Since it is higher than 15.0(1r)SG11, I assume there is no need to upgrade?

[Leo Laohoo]

Ok, so that eliminates the cause why the secondary boot into ROMMON. 

How about the config-registry?  It is set to 0x2101 or 0x2102?

Can you console into the secondary and reboot?  We want to see what it is doing wrong.

[PECET]

Both switches are in 0x2102. I can't console the secondary right now. I'll let you know if someone from the office can. The issue I am encountering right now is I can't get their port-channel status to go UP (both in standalone mode). That is why every time I convert them to mode virtual, they can't see each other and can't establish VSS.

[PECET · Accepted solution]

Hi, I've found the cause of the port-channel not forming. I've encountered this bug here - https://community.cisco.com/t5/cisco-bug-discussions/cscsq36972-portchannel-does-not-form-log-messages-indicate/td-p/2585565

Followed the workaround and it worked. Hope this will be useful for those who would encounter this issue.