User guide

Virtual Chassis Split Protection (VCSP) Configuring Virtual Chassis
page 13-12 OmniSwitch AOS Release 8 Switch Management Guide May 2014
Virtual Chassis Split Protection (VCSP)
In the case of a VC split due to a VFL link failure or the failure of one of the VC elements, both of the
resulting VCs could end up having the same system MAC and IP addresses. Since there is no communica-
tion between these individual VCs due to the VFL link failure they end up communicating with the rest of
the network devices using the same MAC and IP addresses. This split scenario is disruptive to the network
as the conflicting MAC and IP addresses can lead to layer 2 loops and L3 traffic disruption.
VCSP provides the following benefits:
• Avoid network disruptions by preventing duplicate MAC and IP addresses on the network when MAC
retention is enabled and a VC split occurs.
• The sub-VC that forms out of the split is able to detect that a split has occurred.
• Once the VC split condition has been determined, the sub-VC will put its front-panel ports into an
operationally down state preventing traffic forwarding and avoiding loops and possible traffic disrup-
tion. The VCSP link aggregate ports will remain up.
• A trap can be sent by the active-VC indicating the split state. The trap indicates that the split has
occurred and which elements are in the operationally down sub-VC.
• A mechanism is available to recover the non-operational sub-VC.
• A method of detecting a VC split in a remote VC topology where the VC may consist of elements
located in different physical locations such as a remote site, or multiple floors of a building.
VCSP Key Components and Terms
• VCSP PDU - A proprietary packet forwarded between VC elements to help determine that state of the
VC.
• VCSP Helper - A neighboring OmniSwitch, not an element of the VC, responsible for forwarding
VCSP PDUs between the VC elements. The VCSP feature and the VCSP Helper functionality cannot
be enabled on the same switch. The VCSP helper and the VC cannot have the same Group ID.
• VCSP Link Aggregate - A dedicated link aggregate configured between all elements of a VC and a
helper switch to be used for forwarding VCSP PDUs.
• Active-VC - An element, or multiple elements, that results when a VC split occurs. The active-VC will
keep its front panel ports enabled and continue to forward traffic on the network.
• Sub-VC - An element, or multiple elements, that results when a VC split occurs. The sub-VC will
disable its front panel ports to prevent traffic disruption caused by duplicate MAC/IP addresses with
the active VC.
• Protection State - A state an element will transition to after determining a VC split has occurred. Its
ports will be operationally disabled to prevent duplicate MAC and IP addresses and network disruption.
• Guard Timer - A configurable timer determining how long a unit will wait before beginning to send
VCSP PDUs after a VC recovery.