User guide

Configuring Virtual Chassis Virtual Chassis Split Protection (VCSP)
OmniSwitch AOS Release 8 Switch Management Guide May 2014 page 13-13
Basic Operation
When VCSP is enabled, a proprietary protocol runs on a configured link aggregate to carry the VC infor-
mation necessary for VC split detection. Each of the VC elements share a link aggregate with an OmniS-
witch that can act as a helper to assist in the VC split detection.
The lowest member port of the link aggregate hosted on the master element is responsible for sending the
VCSP PDUs on the member link. When the packet arrives on the remote helper device then the helper
device will forward the packet out on all member ports of the link aggregate so that the packet reaches the
remote VC elements.
Use the the virtual-chassis split-protection admin-state and virtual-chassis split-protection linkaggid
commands to enable VCSP and create the VCSP link aggregate on the VC.
Use the the virtual-chassis split-protection helper admin-state and virtual-chassis split-protection
helper linkagg commands to enable the VCSP helper and create the VCSP helper link aggregate on the
helper switch.
Protection States
Under normal VC circumstances the VCSP PDUs are sent once every 3 seconds. When the VC detects a
scenario which leads to a change in its size the protocol sends the VCSP PDUs at a rate of 1 per 50 milli-
seconds for 3 to 10 seconds. This helps to quickly identify a VC split.
On reception of a VCSP frame, the receiving elements match the master of their current VC against the
MAC address of the VCSP sender. If there is a mismatch between the two, then that indicates the pres-
ence of an active VC in the network which is disconnected from the current VC. In this condition the VC
element will monitor 3-5 such consecutive frames, after which it will transition to the protection state.
When an element transitions to the protection state, the following occurs:
• Each of the VC elements will independently transition into the protection state.
• In the protection state each of the VC elements will disable all the user ports except the ones belong-
ing to the VCSP protection link aggregate.
• The VC element will store the protection state transition information in a non-volatile location. This
information will be used whenever an element in the protection state re-boots and needs to check its
current operational state.
• An element in the protection state will send a VCSP PDU back on the link aggregate carrying the
VCSP state as PROTECTION. This is the only frame that is sent by the protection sub-VC. The
purpose of this message is to inform the active-VC to generate an SNMP trap regarding the VC split
state of the VC element.
VC Split Recovery
Once a sub-VC goes into the protection state then all the front panel ports are put into an operationally
down state. There are two ways to recover the VC, manually or automatically.
Manual Recovery
If the guard timer is 0, automatic recovery is disabled and the sub-VC stays in protection mode until the
unit is reloaded by the administrator. After the re-boot the administrator has to manually recover the
switch by first disabling VCSP and then re-enabling VCSP. This clears the protection state variables
stored on the switch.