VSS 6509

[estelamathew]

Hello Friends,

What i m achiving by VSS the same i use to achieve before with 2 redundant core switches, By flowing half vlan's from 1 switch and other half by another core and specifying HSRP priority according to spaning-tree vlan flow, either of them goes other core takesover

What major benefits i m getting by VSS.

Thanks

[Giuseppe Larosa]

Hello Estela,

VSS makes the two C6500 to act a single box and allows to build MEC = multichassis ethernet channel this means that access layer switch can use both uplinks to the two C6500 grouped in a port-channel instead of using a single uplink per vlan.

In server farms this can be a great performance advantage using 2 x10GE instead of 1 10GE.

Hope to help

Giuseppe

[estelamathew]

Hello Giuseppe,

I can use HSRP and spanning tree load balancing among the core switches though they are in active standby VSS, I have read that the packets are forwarded by standby chasis also when they recieve packet in the standby state and it leaves the same switch from where it came, This means that active and standy both are work simultaneously ???? please correct me if i m wrong.

If i m doing vlan priority load balancing among the core switches and also load balancing in HSRP and switches are in vss mode,Is this a proper design to configure the devices in VSS mode???

Thanks

[Leo Laohoo]

With HSRP, you are managing two logical boxes.  With VSS, you manage one logical box.

[Adam Casella]

Hey Matthew,

When running VSS the two chassis are acting as one chassis.  This is done by moving the standby supervisor to another chassis and connecting the two switches together via a link call the Virtual Switch Link.  The VSL extends the back-plane of the 6500 between the two switches on two 10 gig port-channel interfaces.

The VSS gives a few advantages over a regular 6500, but the two largest are:

1.) The configuration is done in one location, so that you do not need to configure two core device, but one.

2.) The failover times for VSS when using MEC (mulit-chassis etherchannel) is couple of hundred milliseconds. Which is vastly improved over HSRP/STP setups.

The MEC is a port-channel that is spannned across the two 6500 chassis (to the far end device it looks like a normal port-channel.  So in other words one link goes to one 6500 chassis and the other link goes to the other 6500 chassis within the VSS.  The improved failover time is achieved because no control plane states change if a failure in one chassis occurs.  If one links fails in the MEC it is equivalent to one link failing in a port-channel.

You can read more about VSS via the following white paper:

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps9336/white_paper_c11_429338.pdf

http://www.cisco.com/en/US/products/ps9336/prod_white_papers_list.html

Also you are correct in saying that a local packet is forwarded by the local switch due to the fact that the forwarding engines are active in each chassis (even though one is standby for control plane traffic).   In other words control plane traffic is handled by one supervisors, but the data plane is handled by both supervisors/chassis's.

I hope this explanation helps clear some items up.

Thanks,

Adam

[estelamathew]

Hello Adam,

All mentioned in above mails i have read before,Just need to clear some points below, I just need a start then i can move ON

Please guide me with any configuration example for spanning tree, and HSRP or GLBP or VRRP, for switches running in VSS mode,

I hope there is no difference for spanning tree configuration and HSRP for example if i want to flow half of the vlan from Active and other half from standby and same i wan to do it for the HSRP i can do it ????? Correct me if i m wrong,

Just write for me 2 commands for spaaning-tree vlan load balancing on 2 switches (1 moving from active and the other moving throgh standby) and same HSRP configuration for these vlan if switches are running in VSS mode.

Thanks

[Adam Casella]

Hey Matt,

No worries, I mis-read your exact question.   In terms of STP, there is little difference between a VSS and standalone chassis.  Think of the VSS as one switch, even though its two chassis's it is logically one switch.   So there is not load-balacing for STP between the chassis's....they are one switch logically.

As for HSRP, this is also not needed between the two chassis's  This would be like configure HSRP on a single switch, there is no benefit.  

VSS uses MEC  to resolve this issue of redundancy.   In order to get everything you need out of VSS you need to use MEC down to your access switches.  Both links in the MEC will be running at all times, just like a normal port-channel.  Therefore if one link fails, or if one chassis fails, you will continue to forward on the other link on the MEC(port-channel).

So with that said, load-balancing between the two chassis's would be done via the port-channel hash on the access switch attached to your MEC.

I think there is a bit of confusions in how the two chassis's are working together.  There is no need to load-balance between them as they are logically one switch.

Thanks,

Adam

[lambay2000]

Hello Dear's,

Very Good Explanation from everybody,,, I have 1 doubt

I want to create a MEC for the attached diagram, I have to apply the port-channel commands on both the chasis ports.

For example the 2 chasis will appear 1 so i have to configure 1/1/1 and also 2/1/1  OR only 1/1/1 ??????

Conclusion from above discussion please reply with YES OR NO if i m wrong and please explain if i m on wrong path.

• Both Switches will appear as 1 switch with additional interface of other standby switch
  
• No Need for HSRP
• Only define spannig tree vlan root commnand as we are working with 1 switch.
  

Any additional hints will be appreciated

[lambay2000]

Hello friends,

Waiting for the confirmation from u experts,,Pls reply.

Thanks