Initialization Procedure - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 5 Configuring Virtual Switching Systems
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If these conditions are unsatisfied, the VSS stops booting and ensures that the forwarding plane is not
performing forwarding. For a description of SSO and RPR, see the
page

Initialization Procedure

The following sections describe the VSS initialization procedure:
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VSL Initialization
A VSS is formed when the two switches and the VSL link between them become operational. Because
both switches need to be assigned their role (VSS Active or VSS Standby) before completing
initialization, VSL is brought online before the rest of the system is initialized. The initialization
sequence is as follows:
1.
2.
3.
4.
5.
The VSS Active switch ensures that the following information matches correctly on both switches:
Switch virtual domain
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Switch virtual node
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Switch priority (optional)
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VSL port channel: switch virtual link identifier
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VSL ports: channel-group number, shutdown, total number of VSL ports
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If the VSS detects a mismatch, it prints out an error message on the VSS Active switch console and
the VSS Standby switch does not bootup. There are various ways to recover from this situation. If
the switch is not running live traffic, you can either disconnect the VSL links or shutdown VSL ports
on the peer, which would boot in VSS Active mode. You can make the necessary changes afterwards
and reboot the switch and ensure VSL links are connected and not put in shutdown mode.
Alternatively, you could clear the VSS rommon variable (VS_SWITCH_NUMBER) and allow the
switch to boot in standalone mode. This method requires that no traffic flows through this switch.
Once the switch is in standalone mode, you can convert it to VSS and then reboot it.
SSO and NSF enabled
SSO and NSF must be configured and enabled on both switches. For detailed information on
configuring and verifying SSO and NSF, see
Supervisor Engine Redundancy."
5-10.
VSL Initialization, page 5-27
System Initialization, page 5-28
VSL Down, page 5-28
The VSS initializes all cards with VSL ports, and then initializes the VSL ports.
The two switch communicate over VSL to negotiate their roles (VSS Active or VSS Standby).
The VSS Active switch completes the boot sequence, including the consistency check described in
the "SSO Dependencies" section on page
If the consistency check completed successfully, the VSS Standby switch comes up in SSO VSS
Standby mode. If the consistency check failed, the VSS Standby switch comes up in RPR mode.
The VSS Active switch synchronizes configuration and application data to the VSS Standby switch.
If VSS is either forming for the first time or a mismatch exists between VSL information sent by the
Standby switch and what is on the Active switch, the new configuration is absorbed in the
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Understanding Virtual Switching Systems
Chapter 13, "Configuring Cisco NSF with SSO
"VSS Redundancy" section on
5-26.
5-27