Cisco Cisco 1700 2600 3600 3700 Series VPN Module White Paper
© 2012 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information.
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Other Supported Modules
Supported interface modules that can coexist within a Cisco Virtual Switching System-enabled chassis include all
CEF720 modules (WS-X6700 series). These modules can also support either a centralized forwarding card (CFC)
or a DFC. If a DFC is installed, it must be compatible with the supervisor PFC operating mode (for example,
PFC3C mode for the Supervisor Engine 720-10G and PFC4 mode for the Superviosr Engine 2T). A lower-mode
DFC inserted in the module will be denied system power until the system-wide PFC mode has been configured and
the system is reloaded.
In a VSS configuration, neither 6100-series nor 6500-series modules are supported. These modules may be
supported in a standalone configuration depending upon the supervisor engine support.
Virtual Switch Link Redundancy
The Virtual Switch Link (VSL) is clearly a vital part of the VSS. It provides the signaling path used for synchronizing
the two supervisor engines’ control planes, as well as providing the data path for any user data traffic needing to
the two supervisor engines’ control planes, as well as providing the data path for any user data traffic needing to
pass between the two chassis. Therefore, the VSL was developed as an EtherChannel interface allowing for
redundant interfaces and higher bandwidth capacity.
Given the hardware requirements discussed in the architecture section of this paper, the VSL must be configured
using specific types of 10 Gigabit or 40 Gigabit Ethernet ports. The main requirement is that the port is capable of
supporting the Virtual Switch Header (VSH) on all traffic traversing the VSL.
One other consideration is the VSL initialization process. VSL interfaces are enabled and initialized very early on
during the system boot process. The reason for this is that the VSL is used to allow the two supervisor engines to
communicate and negotiate the overall VSS control plane redundancy role. This determines which supervisor will
become the VSS active and which will become the standby.
Figure 6. Summary If VSS Initialization Process