7210 SAS-MXP, R6, R12, S, SX, T BASIC SYSTEM
CONFIGURATION GUIDE RELEASE 22.9.R1
Virtual chassis
5.7.6 Adding a new standby CPM node into an existing VC
This scenario is similar to Replacing a standby/active CPM-IMM node with another CPM-IMM node, with
the VC configuration information of the new CPM-IMM node being added to the BOF of the active CPM
node.
5.7.7 Configuration guidelines for upgrading, adding, or removing a VC node
The following configuration guidelines apply for upgrading, adding, or removing a VC node:
• When upgrading an IMM-only node to a CPM-IMM node, ensure connectivity is available between the
IMM and the current active CPM-IMM node over the stacking links.
• A power cycle may be required if the role is changed from a CPM-IMM node to an IMM-only node.
5.8 VC split scenarios
A VC split can occur as a result of the following failures in a VC:
• a single stacking link failure
• a single node failure
• a double failure consisting of two failed links, two failed nodes fail, or a failed link and a failed node
In the event of single stacking link failure in a VC, all nodes including the active and standby CPM-IMM
nodes can continue to communicate with each other. There is no impact on the control plane and no
services are lost because an alternate path exists around the point of failure. Services on all the IMM-only
nodes continue to forward traffic; however, there might be an impact to the switching throughput as the
stacking port bandwidth reduces by half.
Similarly, in the event of a single node failure in a VC, the VC can continue to operate with the active CPM-
IMM node (or the standby CPM-IMM node if the active failed). There is no impact to the control plane or
services and services on all the IMM continue to forward traffic. However, services provisioned on the failed
node are lost and there might be an impact to the switching throughput as the stacking port bandwidth
reduces by half.
If a double failure occurs, because two links fail, or two nodes fail, or a link and a node fail, the VC will have
two islands of nodes/cards. One of these islands needs to own the VC. To decide which island of nodes will
own the VC and continue normal functions, the following occurs:
• If an island has only IMM-only nodes, they all reboot.
• If one of the islands has both active and standby CPM-IMM nodes, nothing happens to the nodes in that
island. They continue to work as normal and services configured on these nodes continue to operate in
the VC without impact. The nodes on the second island reboot.
• If one of the islands has the active CPM-IMM node and the other has the standby CPM-IMM node, the
island with the greater number of nodes continues to be functional in the VC and all the nodes in the
other island reboot. If software determines that the island with the active CPM-IMM is also the island
with the greater number of nodes, that island continues normal operation while the nodes in island with
the standby CPM-IMM all reboot (including the standby node). If software determines that the island
with the standby CPM-IMM is the island with the greater number of nodes, the standby node takes the
role of active CPM-IMM and that island continues operations. The nodes in the other island all reboot.
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