Vss Functionality - Cisco Catalyst 4500 series Administration Manual

Chapter 5 Configuring Virtual Switching Systems
•
•
Multichassis EtherChannel
Beginning with Cisco Release IOS XE 3.5.0E and IOS 15.2(1)SG, Layer 3 MEC is supported on the
Note
Catalyst 4500 series switch. Cisco Release IOS XE 3.4.0SG does not support Layer 3 MEC.
An EtherChannel (also known as a port channel) is a collection of two or more physical links that
combine to form one logical link. Layer 2 protocols operate on the EtherChannel as a single logical
entity. A VSS enables the creation of Multi-Chassis EtherChannel (MEC), which is an Etherchannel
whose member ports can be distributed across the member switches in a VSS. Because non-VSS
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:
•
•
OL-30933-01
service-policy
shutdown
Figure 5-4
VSS with MEC
Redundancy and High Availability, page 5-6
Packet Handling, page 5-6
displays a dual-homed connection for an MEC into the VSS; VSS
VSL
MEC
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)SG
Understanding Virtual Switching Systems
Chassis 2
For information on how
5-5