Sso Dependencies - Cisco Catalyst 4500 series Administration Manual

Chapter 5 Configuring Virtual Switching Systems

SSO Dependencies

For the VSS to operate with SSO redundancy, the VSS must meet the following conditions:
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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.
OL-30933-01
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.
The VSS Active switch ensures that the following information matches correctly on both switches:
Switch virtual domain
–
Switch virtual node
–
– Switch priority (optional)
– VSL port channel: switch virtual link identifier
– VSL ports: channel-group number, shutdown, total number of VSL ports
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."
5-11.
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).
Chapter 12, "Configuring Cisco NSF with SSO
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)SG
Understanding Virtual Switching Systems
"VSS Redundancy" section on
5-27