Data Center Virtualization

[lamav]

When you have a clien thats running VMWare in their server farm, what considerations need to be made with regard to the access layer?

Would having a routed access layer cause complications with certain VMWare features, like VMotion? Where does VMWare need L2 adjacency?

How does the existence of a vSwitch inside the chassis effect the access layer? What consideratiosn should be made?

I know these are loaded questions.

What I need is a data center guide that focuses on the effects of virtualization and the choices one must have to make.

Would love to hear some good feedback.

Thanks

[lamav]

"The access layer could be a 6500 with dual sup-720-vs running SSO.  In  this scenario you uplink one 10Gig port from the primary sup to the VSS  distro and one 10Gig port from the secondary sup to the same VSS distro  using Etherchannel."

Need clarification...from the 6500 access switch with dual SUPs, you run a 10 gig connection from the primary SUP to distro1 and another 10G from the secondary SUP to distro 2. Correct?

Youre saying though that the only switch Cisco makes that supports MEC is the 3750. And you said I would need MEC at the access layer to get VSS to work right. So why would I go with a 6500?

Please make your answers idiot-proof because this is a difficult topic...a loto of options...

Thank you!!

[Reza Sharifi]

Need clarification...from the 6500 access switch with dual SUPs, you run a 10 gig connection from the primary SUP to distro1 and another 10G from the secondary SUP to distro 2. Correct?

That is Correct

Youre saying though that the only switch Cisco makes that supports MEC is the 3750. And you said I would need MEC at the access layer to get VSS to work right. So why would I go with a 6500?

If you have high density need for fiber ports at the access layer.  The Maximum number of fiber ports a 3750 supports is only 12.

HTH

Reza

[lamav]

"If you have high density need for fiber ports at the access  layer.  The Maximum number of fiber ports a 3750 supports is only 12"

OK, that makes sense, but once agin, you said you need an access switch with MEC to support a distro layer with VSS....so what would happen in this case?

[Jon Marshall]

Reza

In order for VSS to work correctly and loop free in the distro, the access layer devices must be capable of doing Multichassis EtherChannel (MEC).

That is interesting because i wasn't aware of this.  I thought that as the 6500 pair appeared as one switch you could use any access-layer switch and uplink to both 6500 chassis using normal etherchannel. There wouldn't be a L2 loop because unlike a normal design where the interconnect between the 6500 switches is counted as one of the L2 paths this isn't the case with VSS.

So are you saying it is recommended to use MEC in access-layer switches with a VSS distro layer or that you can only use MEC ?

Victor, apologies for not getting back, been a bit busy.

Jon

[Reza Sharifi]

Hi Jon,

You don't have to use MEC capable switch only.  Another word if you have a single switch as long as it is capable of utilizing Etherchannel you can uplink 2 ports from it to 2 different distro 6500 (VSS). But if you have multiple switches you can only use 3750s to stack them and have one link from one 3750 and another link from the second 3750 uplink to the VSS pair to create an Etherchannel (MEC) and make it logically look like one switch is connecting to one switch.

Sorry, if I was not clear.

Reza

[Jon Marshall]

sharifimr wrote:
Hi Jon,
You don't have to use MEC capable switch only.  Another word if you have a single switch as long as it is capable of utilizing Etherchannel you can uplink 2 ports from it to 2 different distro 6500 (VSS). But if you have multiple switches you can only use 3750s to stack them and have one link from one 3750 and another link from the second 3750 uplink to the VSS pair to create an Etherchannel (MEC) and make it logically look like one switch is connecting to one switch.
Sorry, if I was not clear.
Reza

Reza

Many thanks for getting back on this.

I should have read your answer more carefully because i missed the bit about using 2 x non MEC switches uplinked to a VSS distro pair. Come to think of it i was being a bit stupid because MEC would be irrelevant with only one switch

In essence with that config ie. a pair of 3560 switches connected to each other and then connected to a VSS pair you have simply inverted the triangle i was referring to in previous post.

So a single non MEC capable switch uplinked to both VSS 6500 switches is fine with no blocking as i understand it ?

Jon

[Reza Sharifi]

Jon,

So a single non MEC capable switch uplinked to both VSS 6500 switches is fine with no blocking as i understand it ?

Yes,

Reza

[lamav]

Hi - sorry it took me so long to get back. Its been a real busy weekend.

Anyway, I have done some reading of my own on VSS and I think I better understand what's going on - at least as far as you can understand without getting your hands on the technology.

In my scenario, in which we have access layer switches uplinked to an aggregation layer running VSS, the MEC functionality is not a function of the access layer switches; it is a function of VSS itself. In other words, you dont need an access switch that supports MEC, per se. Any switch that supports normal etherchannel will be able to be placed in an MEC with a VSS pair.

That was one point that was confusing me. This is possible because the active virtual chassis that includes the active supervisor manages the control-plane and forwards excapsulated messages to the standby switch.

So, as I postulated before, two (2) access switches that are not stacked and are dual-homed to two (2) switches in a distribution layer in a VSS cluster will produce a logical topology that looks like the above (and below) drawing.

Thoughts?

Thanks again

Each access layer switch sees one switch at the distro layer because of  VSS.

                           Disto-virtualized VSS Switch(es)

                                  ||                    ||

                                  ||                    ||

                                  ||                    ||

                         ACCESS  1           ACCESS 2

[Reza Sharifi]

Victor,

Each access layer switch sees one switch at the distro layer because of  VSS.

                           Disto-virtualized VSS Switch(es)

                                  ||                    ||

                                  ||                    ||

                                  ||                    ||

                         ACCESS  1           ACCESS 2

Correct, and the lines connecting the access layer switches to VSS are Portchannels right?

So in this scenario these switches could be any switch as long as they are capable of doing Etherchannel ie 2960, 3560, etc...

HTH

Reza

[lamav]

Hi, Reza...yes, each one of those lines is a single link that [physically] goes to one of the distro switches and they both make up a port channel.

Im glad I got that cleared up. lol

Thanks, man....I may pick your brain more later,. is that OK? Im very happy that you have  alot of practical experience with VSS...

Victor

[Reza Sharifi]

Hi Victor,

No problem at all.  I'll be more then happy to help.

Just as an FYI, today with SXI3 (the latest version of IOS for VSS)  only a single Sup-720-VS is supported per switch.  SXI4 supposed to be released some times in June and according to Cisco it will support 2 Sup-720-VS per chassis.!!!!!

Reza

[SaeedBakh_2]

HI ,

in case we have access switch non Cisco and connected by etherchannel to the two distribution 6509 VSS , still can see the two 6509 VSS as one switch, or because the access switch is not cisco will not be able to see the two 6509 VSS as one switch.

Also if we have two non cisco switches running technology like VSS connected to two cisco 6509 VSS, can cisco and the non cisco see each other as one switch