In Service System Upgrade - ISSU
Use ISSU to upgrade and troubleshoot an active switch with minimal disruption to the network.
ISSU includes the following modes:
In earlier Cumulus Linux releases, ISSU was Smart System Manager.
You can restart the switch in one of the following modes.
cold Restarts the system and resets all the hardware devices on the switch (including the switching ASIC).
fast restarts the system more efficiently with minimal impact to traffic by reloading the kernel and software stack without a hard reset of the hardware. During a fast restart, the system decouples from the network to the extent possible using existing protocol extensions before recovering to the operational mode of the system. The restart process maintains the forwarding entries of the switching ASIC and the data plane is not affected. Traffic outage is much lower in this mode as there is a momentary interruption after reboot, after
warm restarts the system with minimal impact to traffic and without affecting the data plane. Warm mode diverts traffic from itself and restarts the system without a hardware reset of the switch ASIC. While this process does not affect the data plane, the control plane is absent during restart and is unable to process routing updates. However, if no alternate paths exist, the switch continues forwarding with the existing entries with no interruptions.
When you restart the switch in warm mode, BGP performs a graceful restart if the BGP Graceful Restart option is on. To enable BGP Graceful Restart, refer to Optional BGP Configuration.
Cumulus Linux supports fast mode for all protocols; however only supports warm mode for layer 2 forwarding, and layer 3 forwarding with BGP and static routing.
The following command restarts the system in cold mode:
cumulus@switch:~$ sudo csmgrctl -c
The following command restarts the system in fast mode:
cumulus@switch:~$ sudo csmgrctl -f
The following command restarts the system in warm mode.
Warm boot resets any manually configured FEC settings.
cumulus@switch:~$ sudo csmgrctl -w
Upgrade mode updates all the components and services on the switch to the latest Cumulus Linux release without traffic loss. After upgrade is complete, you must restart the switch with either a cold or fast restart.
Upgrade mode includes the following options:
- all runs
apt-get upgradeto upgrade all the system components to the latest release without affecting traffic flow. You must restart the system after the upgrade completes with one of the restart modes.
- dry-run provides information on the components you want to upgrade.
The following command upgrades all the system components:
cumulus@switch:~$ sudo csmgrctl -u
The following command provides information on the components you want to upgrade:
cumulus@switch:~$ sudo csmgrctl -d
Maintenance mode isolates the system from the rest of the network so that you can perform intrusive troubleshooting tasks and data collection or perform system changes, such as break out ports and replace optics or cables with minimal disruption.
- Cumulus Linux supports maintenance mode with BGP, MLAG, and OSPF only.
- Complete isolation depends on your configuration and network topology.
Enable Maintenance Mode
Run the following command to enable maintenance mode. When maintenance mode is on, ISSU performs a graceful BGP shutdown, redirects traffic over the peerlink and brings down the MLAG port link.
switchd maintains full capability.
cumulus@switch:~$ sudo csmgrctl -m1
You can run additional commands to bring all the ports down, then up to restore the port admin state.
cumulus@switch:~$ sudo csmgrctl -p0 cumulus@switch:~$ sudo csmgrctl -p1
Before you disable maintenance mode, be sure to bring the ports back up.
Disable Maintenance Mode
Run the following command to disable maintenance mode and restore normal operation. When maintenance mode is off, ISSU performs a soft restart, runs a BGP graceful restart, and brings the MLAG port link back up.
switchd maintains full capability.
cumulus@switch:~$ sudo csmgrctl -m0
Show Maintenance Mode Status
To see the status of maintenance mode, run the Linux
sudo csmgrctl -s command. For example:
cumulus@switch:~$ sudo csmgrctl -s Current System Mode: Maintenance since Tue Jan 5 00:13:37 2021 (Duration: 00:00:31) Boot Mode: reboot_cold 2 registered modules frr : Maintenance, down switchd : Maintenance, down