Configuring the Cluster Slave Switch Bring-up Process

Note: This feature is applied only during the initial start-up of the cluster slave switch.

When a (previously down) slave node comes back up and a cluster is thus restored to online state, it can take measurable time to change the hardware routing and Layer 2 tables. This set-up delay may cause some non-negligible traffic loss on the network if lots of hardware changes are performed in bulk.

Therefore, to minimize service disruption to a negligible interval, the bring-up process is performed in an optimized staggered fashion by incrementally restoring/updating the ports. (This mode can be changed as shown below.) Some delays are also added during the staggered bring-up to make sure that state transitions and synchronization complete before moving to the next set of changes. (Such delays are configurable as shown below.)

In order to minimize any traffic impact, all non-Layer 3 and non-vLAG ports are restored first. This allows the cluster links to activate and the cluster configuration and state to synchronize.

After synchronization is complete, Layer 3 ports are brought up first. After that, NetVisor OS waits for a configurable l3-to-vlan-interface-delay before bringing up vRouter vlan interfaces. This is so that routing protocols can delay advertising directly-attached subnets upstream.

After Layer 3 ports are brought up, NetVisor OS also waits for another configurable l3-to-vlag-delay to allow time for the routing protocols to converge and program the routes. This time defaults to 15 seconds. After that delay, the vLAG ports are brought up staggered. (Note that l3-to-vlan-interface-delay should be less than or equal to l3-to-vlag-delay.)

The maximum-sync-delay parameter controls the maximum time to wait for synchronization in the case where the cluster cannot synchronize information.

Note that, if the node coming up is a cluster’s master, then no staggering and no Layer 3-to-vLAG delay is applied (because it’s not beneficial). 

With version 5.1.1, NetVisor OS also  supports the staggered bring up of  vRouter VNICs. When configured, the vRouter VNICs, which are not configured on Layer3 ports. are brought up in a staggered manner during the nvOS boot-up on a cluster peer. You can specify the wait time (0-60000 ms) between NIC bring up. 

By default, the vRouter interfaces for which the VLAN is up is brought up simultaneously. The bring up can be staggered by specifying a non-zero vrouter-if-staggered-interval. The staggered bring up process is helpful to reduce the traffic loss caused by the simultaneous bring up of all VNICs.

Note: The vRouter interfaces on Layer 3 ports are brought up first and is not staggered. Also, after bootup, the subsequent VLAN interfaces being down or up is not affected by the  staggered configuration.

In most cases it is not necessary to change the default parameter values. 

However, in certain scenarios to be able to further optimize the slave bring up process to match one’s specific requirements, it is possible to modify the parameters by using the following command:

CLI (network-admin@switch) > cluster-bringup-modify

You can specify one or more of the following options:

l3-port-bringup-mode staggered|simultaneous

Specify the Layer 3 port bring up mode during start up.

l3-port-staggered-interval duration: #d#h#m#s

Specify the interval between Layer 3 ports in Layer 3 staggered mode.  This can be in days, hours, minutes, or seconds.

vlag-port-bringup-mode staggered|simultaneous

Specify the vLAG port bring up mode during start up.

vlag-port-staggered-interval duration: #d#h#m#s

Specify the interval between vLAG ports in vLAG duration: This can be in days, hours, minutes, or seconds.

maximum-sync-delay duration: #d#h#m#s

Specify the maximum delay to wait for cluster to synchronize before starting Layer 3 or vLAG port bring up. This can be in days, hours, minutes, or seconds.

l3-to-vlag-delay duration: #d#h#m#s

Specify the delay between the last Layer 3 port and the first vLAG port bring up. This can be in days, hours, minutes, or seconds. The default value is 15 seconds.

l3-to-vlan-interface-delay duration: #d#h#m#s

Specify the delay between last L3 port and vRouter vlan interface bring up. This can be in days, hours, minutes, or seconds.

port-defer-bringup-delay duration: #d#h#m#s

Specify the global timer value to be used for port delay-bring up.

port-defer-bringup-mode staggered|simultaneous

Specify the port defer bring up mode during start up.

port-defer-bringup-staggered-interval duration: #d#h#m#s

Specify the interval between ports in defer bring up mode.

vrouter-if-bringup-mode staggered|simultaneous

Specify the vRouter VLAN interface bring up mode.

vrouter-if-staggered-interval 0..60000

Specify the interval in ms between vRouter VLAN  interface bring up in staggered mode. The value ranges between 0-60000 ms.

To display the status of the cluster bring up process, use the cluster-bringup-show command:

CLI (network-admin@switch) > cluster-bringup-show

state: ports-enabled

l3-port-bringup-mode: staggered

l3-port-staggered-interval: 3s

vlag-port-bringup-mode: staggered

vlag-port-staggered-interval: 3s

maximum-sync-delay: 1m

l3-to-vlag-delay: 15s

l3-to-vlan-interface-delay: 0s