Cisco 6500 - Manual (Page 25)

4-25
Cisco IOS Software Configuration Guide, Release 12.2SX
OL-13013-06
Chapter 4 Configuring Virtual Switching Systems
Understanding Virtual Switching Systems
VSS initialization is described in the following sections:
• Virtual Switch Link Protocol, page 4-25
• SSO Dependencies, page 4-25
• Initialization Procedure, page 4-26
Virtual Switch Link Protocol
The Virtual Switch Link Protocol (VSLP) consists of several protocols that contribute to virtual switch
initialization. The VSLP includes the following protocols:
• Role Resolution Protocol—The peer chassis use Role Resolution Protocol (RRP) to negotiate the
role (VSS active or VSS standby) for each chassis.
• Link Management Protocol—The Link Management Protocol (LMP) runs on all VSL links, and
exchanges information required to establish communication between the two chassis. LMP
identifies and rejects any unidirectional links. If LMP flags a unidirectional link, the chassis that
detects the condition brings the link down and up to restart the VSLP negotiation. VSL moves the
control traffic to another port if necessary.
SSO Dependencies
For the VSS to operate with SSO redundancy, the VSS must meet the following conditions:
• Identical software versions—Both supervisor engine modules on the VSS must be running the
identical software version.
• VSL configuration consistency—During the startup sequence, the VSS standby chassis sends virtual
switch information from the startup-config file to the VSS active chassis. The VSS active chassis
ensures that the following information matches correctly on both chassis:
– Switch virtual domain
– Switch virtual node
– Switch priority
– VSL port channel: switch virtual link identifier
– VSL ports: channel-group number, shutdown, total number of VSL ports
– Power redundancy-mode
– Power enable on VSL modules
If the VSS detects a mismatch, it prints out an error message on the VSS active chassis console and
the VSS standby chassis comes up in RPR mode.
After you correct the configuration file, save the file by entering the copy running-config
startup-config command on the VSS active chassis, and then restart the VSS standby chassis.
• PFC mode check—If both supervisor engines are provisioned with PFC3C, the VSS will
automatically operate in PFC3C mode, even if some of the switching modules are equipped with
DFC3CXLs.
However, if the supervisor engines are provisioned with PFC3CXL and there is a mixture of DFC3C
and DFC3CXL switching modules, the system PFC mode will depend on how the 3C and 3CXL
switching modules are distributed between the two chassis.