Vss Initialization - Cisco Catalyst 4500 Series Software Configuration Manual

Understanding Virtual Switching Systems
In this scenario, if switch 1 enters recovery mode, it will use IP1 for the fa1 interface on switch 1.
Conversely, if switch 2 enters recovery mode, it will use IP2 for the fa1 interface on switch2.
Scenario 2
The VSS system is configured as follows:
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In this scenario, if switch 1 enters recovery mode, it will use IP1 for the fa1 interface on the switch 1.
Conversely, if switch 2 enters recovery mode, it will use GIP for the fa1 interface on switch2.

VSS Initialization

A VSS is formed when the two switches and the VSL link between them become operational. The peer
switch communicates over the VSL to negotiate the switches' roles.
If only one switch becomes operational, it assumes the VSS Active role. The VSS forms when the second
switch becomes operational and both switches bring up their VSL interfaces.
VSS initialization is described in the following sections:
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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:
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SSO Dependencies
For the VSS to operate with SSO redundancy, the VSS must meet the following conditions:
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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
5-26
Global IP address - GIP
switch 1 IP address - IP1
switch 2 specific IP address
Virtual Switch Link Protocol, page 5-26
SSO Dependencies, page 5-26
Initialization Procedure, page 5-27
Role Resolution Protocol
The peer switch use Role Resolution Protocol (RRP) to negotiate the role (VSS Active or VSS
Standby) for each switch.
Link Management Protocol
The Link Management Protocol (LMP) runs on all VSL links, and exchanges information required
to establish communication between the two switches.
LMP identifies and rejects any unidirectional links. If LMP flags a unidirectional link, the switch
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.
Identical software versions (except during ISSU with compatible versions)
VSL configuration consistency
During the startup sequence, the VSS Standby switch sends virtual switch information from the
startup-config file to the VSS Active switch.
Chapter 5 Configuring Virtual Switching Systems