Vss Functionality - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 5 Configuring Virtual Switching Systems
switches connected to a VSS view the MEC as a standard EtherChannel, non-VSS switches can connect
in a dual homed manner.
is seen as a single logical switch. Traffic traversing an MEC can be load balanced locally within a VSS
member switch much as in standard EtherChannels. Cisco MEC supports the bundling protocols LACP
and PAgP as well as ON mode.
Figure 5-4
Chassis 1
VSS supports a maximum of 256 EtherChannels. This limit applies to the total number of regular
EtherChannels and MECs. Because the VSL requires two EtherChannel numbers (one for each switch
in the VSS), there are 254 user-configurable EtherChannels.
For information on how to configure Layer 3 Multichassis EtherChannels, see
to configure Layer 3 Multichassis EtherChannels, see, page 5-5

VSS Functionality

The following sections describe the main functionality of a VSS:
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Redundancy and High Availability
In a VSS, supervisor engine redundancy operates between the VSS Active and VSS Standby switch,
using stateful switchover (SSO) and nonstop forwarding (NSF). The peer switch exchange configuration
and state information across the VSL and the VSS Standby supervisor engine runs in SSO-HOT mode.
The VSS Standby switch monitors the VSS Active switch using the VSL. If it detects failure, the VSS
Standby switch initiates a switchover and takes on the VSS Active role. When the failed switch recovers,
it takes on the VSS Standby role.
Figure 5-4
VSS with MEC
Redundancy and High Availability, page 5-5
Packet Handling, page 5-6
System Management, page 5-6
Quad-Supervisor (In-chassis Standby Supervisor Engine) Support, page 5-6
Asymmetric chassis support, page 5-7
Interface Naming Convention, page 5-7
Module Number Convention, page 5-7
Key Software Features not Supported on VSS, page 5-7
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
displays a dual-homed connection for an MEC into the VSS; VSS
VSL
MEC
Understanding Virtual Switching Systems
Chassis 2
For information on how
5-5