Jaycee's Networking

July 1, 2009

Virtual Switching System (VSS)

Filed under: Information, IOS — Tags: , — Jaycee @ 7:22 pm

A. VSS (Virtual Switching System)

1. VSS pools multiple Catalyst 6500 switches into one virtual switch, increasing bandwidth capacity to 1.4 Tbps.

2. A VSS will allow 2x 6500 to operate as a single logical virtual switch called VSS1440.

3. VSS1440 = 2x 6500 with SUP720-10GE

4. In a VSS, the data plane and switch fabric with capacity of 720 Gbps of supervisor engine in each chassis are active at the same time on both chassis, combining for an active 1400-Gbps switching capacity per VSS. But

a. ONLY ONE of the virtual switch members has the active control plane.

b. Both chassis are kept in sync with the SSO (Stateful Switchover) mechanism along with NSF (Nonstop Forwarding) to provide nonstop communication.

5. Benefits:

a. single point of management, IP address, and routing instance for 6500 virtual switch

1) single configuration file and node to manage.

2) removes the need to configure redundant switches twice with identical policies.

3) Only one gateway IP address is required per VLAN instead of the 3 IP address per VLAN used today.

4) removes the need for HSRP, VRRP, GLBP

*Cisco LMS (LAN Management System) 3.0 can be used to centrally manage a 6500 virtual switch as a single entity

b. MEC (Multichassis EtherChannel) is a Layer 2 multipathing technology that creates simplified loop-free toplogies, eliminating the dependency on STP. (STP can still be activated to protect strictly against any user misconfiguration.)

c. Flexible deployment – physical switches don’t have to be colocated: 2 physical switches are connected with standard 10 Gigabit Etherent interfaces and as such can be located any distance based on the distance limitation of the 10Gigabit Etherenet optics.

d. VSS eliminates L2/L3 protocol reconvergence if a virtual switch member fails

e. VSS scales system bandwidth to 1.4Tbps:

1) activates all L2 bandwidth across redundant 6500 switches with automatic load sharing.

2) maximizing server bandwidth throughput

f. eliminating unicast flooding caused by asymmetrical routing in traditional campus designs

g. optimizing the number of hops for intracampus traffic using multichassis EtherChannel enhancements

6. Target deployment areas for VSS:

a. Campus or DC core/distribution layer

b. DC access layer (server connectivity)

7. Two physical chassis doesn’t need to be identical in the type of modules installed or even type of chassis. For example, a WS-C6503-E chassis can be combined with a WS-C6513 chassis to form a VSS.

8. eFSU (enhanced fast software upgrade) is a mechanism to perform software upgrades while maintaining HA. It leverages the existing features of NSF and SSO and significantly reduces the downtime to less than 200ms.

9. Dual active state is detected rapidly by:

a. Enhancement to PAgP used in MEC with connecting Cisco switches

b. L3 BFD (Bidirectional Forwarding Detection) configuration on a directly connected link between virtual siwtch memebers or through an L2 link through an access layer switch.

c. L2 Fast-Hello Dual-Active Detection configuration on a directly connected link between virtual switch members.

B. MEC (Multichassis EtherChannel)

1. MEC allows a connected node to terminate the EtherChannel across the 2 physical Catalyst 6500 switches that make up the VSS leading to creating simplified loop-free L2 toplogy.

2. Using MEC in VSS topology results in all links being active and at the same time provides for a highly available topology without the dependency of STP.

3. supports up to 512 MECs.

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3 Comments »

  1. I love what you guys are up too. Such clever work and exposure!
    Keep up the amazing works guys I’ve incorporated you guys to our blogroll.

    Comment by Emmett — August 2, 2013 @ 8:11 am

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    Comment by best ac service miami fl — February 17, 2014 @ 10:02 am

    • no. i dont. thank you!

      Comment by Jaycee — February 26, 2014 @ 12:43 am


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