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Best Practices on Wireless upgrade of WiSM in redundant environment

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Introduction

The Cisco Wireless Services Module WiSM is a WLAN controller services module for the Cisco Catalyst 6500 Series modular switches and Cisco 7600 Series routers. It works with Cisco Aironet  Series lightweight access points, the Cisco Wireless Control System (WCS), and the Cisco Wireless Location Appliance to deliver a secure and unified wireless solution that supports mission-critical wireless data, voice, and video applications.

In this Scenario, Software upgrade of WiSM in our WiFi environment, two 6500 series chassis loaded with 5 WiSMs' each. In that, 1 chassis is acting as primary and 1 chassis is acting as secondary. The WiSMs are fully loaded with access points. What will be the best option, whether to upgrade WiSMs' in redundant chassis first or the ones in primary chassis first.

  • Lets consider, we finished upgrading WiSMs' in redundant chassis, when they are empty. Then When we upgrade Primary chassis WiSMs' and reload them, The APs will failover to redundant chassis's WiSMs. Then APs will try to upgrade them with new version. Meanwhile the Primary Chassis' WiSMs come up after booting with new image. AP fall back is enabled.
  • Whether the AP will try to fallback to primary WiSM, when it is in downloading image stage in secondary chassis? or the AP will not fallback until completion of downloading and registration process in secondary controller?

Solution

We can use ap predownload. It saves alot of time, since the WISM is limited to how many aps it can upgrade at a time. It can be sitting for a good bit waiting for aps to upgrade.

In large environment with 3000 aps up and down in 3 minutes with ap predownload.

If we push the code to the WLC, we can then push the code to the APs. When we reboot the controller they will all come up with the new code. No need to wait for downloading. No need for templates.

Important things to Remember

  • Push the code to the controllers when there is less folks on the wireless. When the code unpacks on the WLC you will see some aps lose connection to the controllers. This is known (among people who pay close attention to their logs), but not widely if at all documented. The aps lose their capwap connection for a second or so. Its like a blip to the user

  • Do the predownload process hours before your actual cut over time. It can take a full wism 300 aps like and hour or more to predownload the new code.

  • Code Swap on the wlc and ap. If you don't have the software in the right position you could indeed cause the aps to download code again after your reboot.

So make sure you swap the ap code and the controller code correctly before reboot! Also if you predownload the code to the WLC and APs well in advance of the upgrade. Make sure you put the codes in the backup on the wlc and aps. If not, and a wlc accidentally reboots you will have a little problem on your hands.

  • Make sure you reboot all the WLCs at the same time. Use the config system reset at command in the cli or in the GUI. Make sure your wlcs all have the same time before doing this.

Alternatively

  1. Upgrade the firmware and bootstrap of the secondary WiSM.
  2. Move all the WAPs to the secondary. (Several ways of doing this. Primarily if you have WCS/NCS then this is the way to go. If you don't then either disable or BLOCK the allowed VLAN to your Management address from your primary WiSM chassis. This will forcefully send the WAPs to the secondary WiSM.)
  3. Once you have confirmed that all the WAPs are fully accounted for, then upgrade the firmware and bootstrap of the primary WiSM.
  4. IF you don't have WCS/NCS then enable the Management VLAN.

If you have "pre-download" option, then this will save you time.

Another thing is this: Newer IOS of the 7.0.X have the option to schedule the reboot of your WiSM. So maybe you can enable this option.

Redundancy FAQ

Q. What happens if a Cisco WiSM fails?
A. Similar to a cluster of Cisco wireless LAN controllers, if the first controller on the Cisco WiSM fails, the access points will fail over to the second Cisco WiSM controller, or a secondary or tertiary controller, either in the same chassis or a separate chassis, depending on the redundancy architecture defined by the IT staff.


Q. Can the Cisco WiSM be automatically rebooted upon failure?
A. Yes. When a Cisco Catalyst Supervisor Engine 720 detects a Cisco WiSM failure, it waits three minutes to see if the Cisco WiSM comes back online. If the Cisco WiSM does not come back online within the three-minute time period, the Supervisor Engine 720 reboots the Cisco WiSM.


Q. Does the Cisco WiSM support N:1 redundancy?
A. Yes. The Cisco WiSM supports N:1 controller redundancy for single module failures. If a Cisco WiSM controller fails, the access points automatically fail over to an alternate Cisco WiSM or Cisco wireless LAN controller.


Q. Does the Cisco WiSM support access point redundancy?
A. Yes. The Cisco WiSM supports access point redundancy. If an access point fails, the Cisco WiSM automatically increases power on the neighboring access points to compensate and provide coverage.

Reference

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