Cisco WS-X6708-10G-3CXL= - 10 Gigabit Ethernet Module Uživatelský manuál stáhnout pdf (Strana 9)

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The VSL is both the enabling technology of the Cisco Virtual Switching System and a critical link of the system.

Internal Cisco Catalyst 6500 control information that is usually retained within the chassis must now be exchanged

across the VSL to the peer switch, extending the backplane between the two switches. You should, therefore, always

provision the VSL to contain at least two member links, which should be deployed along different physical paths or

conduits. You should minimize data traffic use of the VSL wherever possible. Refer to the section “Cisco

EtherChannel Concepts” for more details.

Control-Plane Communication

The VSL is crucial for both CPUs in each supervisor engine to communicate with each other. It is also used to

determine which virtual switch becomes the active virtual switch and which becomes the standby virtual switch.

Because this determination affects the behavior of each switch, the roles must be negotiated very early during the

chassis bootup cycle. As a result, the system must bring the VSL and its associated ports online before initializing the

rest of the system.

Communication between the two chassis is facilitated with internal messaging that is sent across the VSL. Because

the VSL is implemented as a Cisco EtherChannel interface, it is resilient to single-link failures. However, realistically

only a single link of the VSL is chosen as the control link at any given time because the hash algorithm of the Cisco

EtherChannel interface is based on the source and destination MAC addresses, which are always the same for each

CPU.

Virtual Switch Link Initialization

The system must bring the VSL online before activating the Cisco Virtual Switching System. The initialization

sequence consists of the following steps:

1. In-chassis Role Resolution

Beginning in software release 12.2(33)SXI4 the Virtual Switching System may be configured with two supervisor

modules in a single chassis. If the chassis is configured with two supervisors then the two supervisors start their

boot process by performing role negotiation. This initial role negotiation is to determine which supervisor will

become the active supervisor for the chassis. One Supervisor will become the In-chassis Active and the other

will become the In-chassis Standby. The In-chassis Active will continue to boot as a supervisor module and

proceed with the VSL initialization. Alternatively, the In-chassis Standby supervisor will boot to a VSS unique

redundancy mode which allows it to perform primarily as a line card but with some data synchronized for

redundancy. More details on the In-chassis redundant supervisor are provided in the High Availability section of

this paper.

2. VSL initialization

The VSL link initialization occurs very early in the system boot cycle—it actually occurs even before the

configuration file is parsed and the system is initialized. To determine which ports form members of the VSL, the

configuration file is preparsed to extract the appropriate VSL commands and their associated interfaces, so that

the modules containing these interfaces can be powered up, diagnostics run, and VSL interfaces brought online.

The Link Management Protocol (LMP) operates on each link of the VSL and is part of the Virtual Switch Link

Protocol (VSLP). It performs the following functions:

◦ Identifies and rejects unidirectional links

◦ Exchanges switch IDs between the two chassis

◦ Exchanges other information required to establish communication between the two chassis

3. VSS Role resolution

The role of each physical chassis is resolved by another protocol that forms part of VSLP—the Role Resolution

Protocol (RRP), which performs the following functions:

●

Determines whether the hardware and software versions allow a Cisco Virtual Switching System to be formed

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