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Trunk Mode Off After 9.3 Upgrade

admindude
Level 1
Level 1

Hi all, first time poster here looking for some direction on a config.

We upgraded a 9148S from 8.3(2a) to 9.3(2) - latest supported version and after the upgrade I noticed a few ports that before had the Trunk On.

fc1/1 is up
Port description is client_fc1
Hardware is Fibre Channel, SFP is short wave laser w/o OFC (SN)
Admin port mode is auto, trunk mode is off

interface fc1/1
switchport description client_fc1
switchport trunk mode off
port-license acquire
no shutdown

Would want to understand why these are moved offline during the upgrade and if I should move them back one by one to online?

Looking at the MDS Guide I see the following note: "You will see the switchport trunk mode off command added to F ports after upgrading from Cisco MDS NX-OS Release 8.1(1) to Cisco MDS NX-OS Release 8.2(1). " but not a whole lot explanation about it and what to do.

I appreciate the time taken with my question.

 

2 Replies 2

balaji.bandi
Hall of Fame
Hall of Fame

Looks like that is default set to off, you need to manually turn on (i guess) what is the outcome if you make then on manually.

 

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zawoo
Cisco Employee
Cisco Employee

It is an expected behavior. The trunk mode will be set to OFF during ISSU and during the "reload system non-disruptive" since it will follow the same ISSU path.

This change was implemented since the NX-OS 4.x to address the below two cases:

  1. Since the support for F-port trunking and F port-channels are added in 4.x, if the user upgrades from 3.x to 4.x and if a link flaps, the trunk mode will be on and the switch will try to run the protocols and try to bring up the port in F-port trunking mode, but a user may not intend this behavior. To avoid running the trunking protocols, we are disabling the trunk mode to off.
  2. It is noticed that there are some HBAs where they are setting VF bit = 1 in the FLOGI even though they are regular HBAs that don't support F-port trunking. To avoid any traffic disruption for the user, after the upgrade followed by a link flap, we change the trunk mode to OFF if the user has never touched the trunk mode config on this port.

Also, there should not be any impact on the system/host with this change.

Trunk mode change will happen only when the following conditions are met: 

  1. The user has never touched the trunk mode config ("show port internal info interface fcx/x" should have "user_cfg_flag" set to 0x1. This will be the default state when we do a write erase reload).
  2. The device has not set a VF bit in the flogi request ("VF tagging not capable" in "show port internal info interface fcx/x").
  3. The operational mode for the port is F or FL.
  4. The port should be in the UP state.

Regarding the configuration guide, we had requested to make it generic since the change could happen if you upgrade from any release to any other higher release versions and if the above four conditions are met.

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