Cisco Catalyst 4500 Series Software Configuration Guide

12-3
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 12 Configuring Supervisor Engine Redundancy Using RPR and SSO on Supervisor Engine 7-E, Supervisor
About Supervisor Engine Redundancy
Note Persistent configuration includes the following components: startup-config, boot variables,
config-register, and VLAN database.
The standby supervisor engine pauses the startup sequence after basic system initialization, and in the
event that the active supervisor engine fails, the standby supervisor engine becomes the new active
supervisor engine.
In a supervisor engine switchover, traffic is disrupted because in the RPR mode all of the physical ports
restart since there is no state maintained between supervisor engines relating to module types and
statuses. Upon switchover, when the standby supervisor engine completes its initialization, it will read
hardware information directly from the module and become the active supervisor engine.
SSO Operation
SSO is supported in Cisco IOS-XE Release 3.1.0SG and later releases. When a standby supervisor
engine runs in SSO mode, the standby supervisor engine starts up in a fully-initialized state and
synchronizes with the persistent configuration and the running configuration of the active supervisor
engine. It subsequently maintains the state on the protocols listed below, and all changes in hardware
and software states for features that support stateful switchover are kept in synchronization.
Consequently, it offers zero interruption to Layer 2 sessions in a redundant supervisor engine
configuration.
Because the standby supervisor engine recognizes the hardware link status of every link, ports that were
active before the switchover will remain active, including the uplink ports. However, because uplink
ports are physically on the supervisor engine, they will be disconnected if the supervisor engine is
removed.
If the active supervisor engine fails, the standby supervisor engine become active. This newly active
supervisor engine uses existing Layer 2 switching information to continue forwarding traffic. Layer 3
forwarding will be delayed until the routing tables have been repopulated in the newly active supervisor
engine.
After a switchover, Access Point (AP) connected ports take some time to converge. For faster STP
convergence of AP connected ports, enable the spanning-tree portfast edge interface configuration
command on all interfaces that are connected to APs. This enables the workstation or server to allow
those devices to connect to the network immediately, rather than waiting for spanning tree to converge.
SSO supports stateful switchover of the following Layer 2 features.
The state of these features is preserved between both the active and standby supervisor engines:
• 802.3
• 802.3u
• 802.3x (Flow Control)
• 802.3ab (GE)
• 802.3z (Gigabit Ethernet including CWDM)
• 802.3ad (LACP)
• 802.1p (Layer 2 QoS)
• 802.1q
• 802.1X (Authentication)

Cisco Catalyst 4500 Series Specifications

General

Series	Catalyst 4500 Series
Category	Switch
Layer Support	Layer 2, Layer 3
Form Factor	Modular chassis
Stackable	No
Chassis Slots	3, 6, 7, 10
Power Supply Options	AC, DC
Redundancy	Power supply, Supervisor engine
Network Management	Cisco IOS Software CLI, SNMP, Cisco Prime Infrastructure
Features	Security, QoS
Port Density	Up to 384 ports per chassis
Security Features	802.1X, ACLs, DHCP Snooping, Dynamic ARP Inspection, IP Source Guard
Supervisor Engine	8-E