Ask Me Anything Event
Welcome to the Cisco Community Ask Me Anything conversation. Submit your questions from Monday, October 14, 2024 through Friday, October 28, 2024. Our colleagues Saikat Nandy, Parithosh Vema and Naveen Kumar will be waiting to assist you and resolve any questions that have not been clarified, or answer any new questions that you may have. We are waiting for you!
More about this event:
Join us for an Ask Me Anything (AMA) event where you can dive deep into Cisco Catalyst 9800 Upgrade and High Availability!
What is it?
The Cisco Catalyst 9800 Series (C9800) is the next-generation wireless LAN controller from Cisco. It has been built from the ground up to support today's most demanding wireless networking requirements. They are designed with an open and programmable operating system to provide flexibility of management and automation. The platform is having built-in class features which can reduce your maintenance window downtime and at the same time it can provide the required resiliency and redundancy to your mission-critical wireless network.
- N+1 Hitless Upgrade: Hitless upgrade leverages the concept of N+1 high availability with a spare WLC (already upgraded to the target version) to upgrade the CAPWAP infrastructure. The APs are then upgraded in a staggered fashion using the Rolling AP upgrade feature, which avoids network disruption and does not allow all the APs upgrade at once. This ensures that the clients are serviced by the neighbour APs while one of the APs undergoes the upgrade process.
- ISSU Upgrade: In-Service Software Upgrade (ISSU) is a procedure to upgrade a wireless controller image to a later release while the network continues to forward packets. ISSU helps network administrators avoid a network outage in a critical environment (Ex - Hospital) while performing a software upgrade.
- HA-SSO: High availability has been a requirement on wireless controllers to minimize downtime in live networks. High Availability - Stateful Switchover (HA-SSO) capability of a wireless controller allows the access point to establish a CAPWAP tunnel with the Active wireless controller and the Active wireless controller to share a mirror copy of the AP and client database with the Standby wireless controller. The APs do not go into the Discovery state and clients do not disconnect when the Active wireless controller fails and the Standby wireless controller takes over the network as the Active wireless controller. There is only one CAPWAP tunnel maintained at a time between the APs and the wireless controller that is in an Active state.
- AP Image Predownload: To minimize network outages, download an upgrade image to an access point from the WLC(already having the upgrade image) without resetting the access point or losing network connectivity. If followed, this step significantly decreases the MW timeline while performing regular upgrade. In a flex environment, the same mechanism can be performed through efficient image upgrade in a slightly different way.
Official Resources:
Regular Upgrade - https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/17-12/config-guide/b_wl_17_12_cg/m_upgrade_9800cl.html
N+1 Hitless Upgrade - https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/215550-hitless-software-upgrade-on-catalyst-980.html
ISSU Upgrade - https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/17-12/config-guide/b_wl_17_12_cg/m_issu.html
High Availability - 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
AP Image Predownload - https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/17-12/config-guide/b_wl_17_12_cg/m_predwnld_image_ap_ewlc.html
Efficient Image Upgrade - https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/17-12/config guide/b_wl_17_12_cg/m_eff_image_upgrade_ewlc.html
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Our experts
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Saikat Nandy
Technical Consulting Engineer
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Parithosh Verna Technical Consulting Engineer |
Naveen Kumar Technical Consulting Engineer |
In the 9800 HA, the Active and Standby unit operates as a single unit so the Standby unit is expected to have its physical interfaces in the down state while the Active is running the network. GW(gateway) Reachability is done independently from both Active & Standby via the RMI (Redundancy Management Interface), so although the physical interfaces of the Standby WLC will be DOWN(on the switch connecting to the standby will be UP), the SVI with the RMI IP address will stay up and that is used as the source when the gateway check is done.
If you see the working of the Default Gateway Check:
Default Gateway check is done by periodically sending Internet Control Message Protocol (ICMP) ping to the gateway. Both the active and the standby controllers use the RMI IP as the source IP. These messages are sent at 1 second interval. If there are 8 consecutive failures in reaching the gateway, the controller will declare the gateway as non-reachable.
Refer page 27 in the HA deployment guide for more context: https://www.cisco.com/c/dam/en/us/td/docs/wireless/controller/9800/17-1/deployment-guide/c9800-ha-sso-deployment-guide-rel-17-1.pdf
