Cisco 6500 - Manual (Page 11)

4-11
Cisco IOS Software Configuration Guide, Release 12.2SX
OL-13013-06
Chapter 4 Configuring Virtual Switching Systems
Understanding Virtual Switching Systems
Understanding VSL Topology
A VSS contains two chassis that communicate using the VSL, which is a special port group.
We recommend that you configure both of the 10-Gigabit Ethernet ports on the supervisor engines as
VSL ports. Optionally, you can also configure the VSL port group to contain switching module
10-Gigabit Ethernet ports. This configuration provides additional VSL capacity. See
Figure 4-6 for an
example topology.
Figure 4-6 VSL Topology Example
VSS Redundancy
The following sections describe how redundancy in a VSS supports network high availability:
• Overview, page 4-11
• RPR and SSO Redundancy, page 4-12
• Failed Chassis Recovery, page 4-13
• VSL Failure, page 4-13
• User Actions, page 4-14
Overview
A VSS operates stateful switchover (SSO) between the VSS active and VSS standby supervisor engines.
Compared to standalone mode, a VSS has the following important differences in its redundancy model:
• The VSS active and VSS standby supervisor engines are hosted in separate chassis and use the VSL
to exchange information.
• The VSS active supervisor engine controls both chassis of the VSS. The VSS active supervisor
engine runs the Layer 2 and Layer 3 control protocols and manages the switching modules on both
chassis.
• The VSS active and VSS standby chassis both perform data traffic forwarding.
If the VSS active supervisor engine fails, the VSS standby supervisor engine initiates a switchover and
assumes the VSS active role.
Active
Supervisor
Linecard 1
Linecard 2
Linecard N
Standby
Supervisor
Linecard 1
Linecard 2
Linecard N
Active chassis Standby chassis
181326
VSL