We discussed the VSS on Cisco Catalyst 4500 and 6500 several times before. And with the software update, there are some new points that happened on Cisco Catalyst 4500 VSS. What’s new here? Let’s read some simple questions that cam make you clear about it.
VSS (Virtual Switching Systems) combines a pair of Cisco Catalyst 4500 or 4500-X series switches into a single network element. It requires 2 chassis with 2 supervisors; the benefit is not only for the chassis redundancy, but also to double the system bandwidth in order to increase overall system performance.
The following table describes the hardware requirements for the VSS chassis and modules.
VSS Hardware Requirements
| Hardware | Count | Requirements |
| Chassis | 2 | VSS is available on a Catalyst 4500-X switch and on chassis that support Supervisor Engine 7-E, Supervisor Engine 7-LE, and Supervisor Engine 8-E.
Note +E and -E chassis can be mixed. |
| Supervisor Engines | 2 | VSS is available on Supervisor Engine 7-E, Supervisor Engine 7L-E, Supervisor Engine 8-E, and on the Catalyst 4500-X switch series.
All supervisor engines or systems in a VSS must match precisely. |
| Linecard | 0 to as many linecard slots are available in a chassis. | WS-X4712-SFP-E
WS-X4724-SFP-E WS-X4748-SFP-E WS-X4748-RJ45V+E WS-X4640-CSFP-E WS-X4748-RJ45-E WS-X4606-X2-E WS-X4648-RJ45V-E WS-X4648-RJ45-E WS-X4624-SFP-E WS-X4612-SFP-E WS-X4548-RJ45V+ WS-X4448-GB-SFP WS-X4306-GB WS-X4248-RJ45V WS-X4248-FE-SFP WS-X4148-RJ WS-X4148-FX-MT |
You can use 1 GE and 10 GE links as VSL EtherChannel members, but you cannot mix 1 GE and 10 GE ports in one EtherChannel.
What are the key software features? With some exceptions, the VSS maintains feature parity with the standalone Cisco Catalyst 4500 and 4500-X series switches.
The following are the major exceptions (including after the release of Cisco IOS XE 3.7.1E):
● IPv6 source guard, IPv6 prefix guard, and data-glean on EtherChannels
● CFM D8.1
● EnergyWise Management Suite
● Fast UDLD
● Flexlink
● Mediatrace (Medianet active video monitoring feature)
● Metadata (Medianet feature)
● Per VLAN Learning
● REP and associated featurettes
● UDE
● UDLR
● VMPS Client
● Wireless Controller
More Simple FAQ to Tell You the New Features of Catalyst 4500 VSS
Can I configure a VSS between chassis of different slot capacities? Yes, a VSS between chassis of different slot capacities works fine. However, note that +E and -E chassis cannot be mixed.
Can I have VSSs across different types of Supervisor Engines? No. The supervisors need to be of same type with same software version.
The maximum configurable number of multichannel EtherChannels (MEC) per VSS is 256.
Can you point me to a document that discusses VSS traffic convergence? Here is a good document that talks about traffic recovery and convergence time during VSS component failures. Note that though the design best practices remain the same between the Catalyst 4500 VSS and Catalyst 6500 VSS, the actual convergence times may vary between the two platforms.
Can the 4500 VSS support long-distance virtual switch link (VSL)? Yes, the optics supported in the standalone chassis are supported for VSL with the same cable length support.
- A standalone Catalyst 4500 supports 64 EtherChannels.
- A VSS supports 256 EtherChannels.
Which dual-active detection modes are supported? The Cisco Catalyst 4500 VSS supports two methods: Enhanced PAgP and Fast-Hello, for detecting a dual-active scenario. For more details, refer the following link:
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/XE3-7-0E/15-23E/configuration/guide/xe-370-configuration/vss.html#pgfId-1063718
Do I need to configure both dual-active modes? No, using only one dual-active detection method is fine.
What is the status of the standby Supervisor Engine in a VSS chassis? In VSS mode, a single chassis supports a second Supervisor Engine, but only in ROMMON mode.
This In-Chassis-Standby (ICS) cannot take part in high-availability configurations; only the uplinks ports are usable for forwarding traffic.
What is Easy-VSS? It’s a feature that enables you to configure VSS with a single command on the active switch and no action needed on the VSS standby switch. For more detail, refer the following link:
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/XE3-7-0E/15-23E/configuration/guide/xe-370-configuration/vss.html#pgfId-1480723
Can I mix 16 ports and 32 ports in a 4500-X VSS pair? No, the 4500-X should be of same type in a VSS pair.
PDF File from https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-4500-series-switches/q-and-a-c67-734489.pdf
More Related VSS Topics
Cisco VSS Configuration: Cisco Catalyst 6500 Virtual Switching System
A Sample VSS Configuration for 2x Cisco Cat6500 with Supervisor 720
