VSS (Core) and vPC (Distrubution)

[Network Pro]

Hi 

is it possible to run VSS(Core) layer - like 6500 and have another set of switches like N5k/7k as distrubution running vPC ? I just need to extend the vlans onto N5k/7k and these switches will be having few servers directly connected to them (Server/host vPC)

There will be 1 link to each distribution switch N5k (or7k) from core switch - how will the connections be from Core to Distribution and how will the config look like ? does that need to vPC or can it be straight port channel

6500-1------VSS-------6\500-2

|                                     |

|                                     |

N5k1------vPC---------N5k2

|                                    |

|-----------Server----------|

[Mark Malone]

Yes just standard po on vss side and vpc on the nexus side , heres a guide of it setup

http://dustydev.blogspot.com/2012/10/configuring-vss-cisco-6500-and-vpc.html#!/2012/10/configuring-vss-cisco-6500-and-vpc.html

[Network Pro]

Thanks Mark, does it need vPC on Nexus side or can i be only straight Port channel ?

the reason i ask is because if i do port channel with a single link to Core switch from each nexus then it means it will have to use the peer-link right since there is no second link to 2nd core ?

I am not running any routing protocol on Nexus (just distribution switches extending the vlan of core)

[Mark Malone]

i haven't tested that i do have standard switches running pos with vpc on the 5ks side directly connected by 10gb works fine so i know the vpc to standard po will work fine for you

the reason i ask is because if i do port channel with a single link to Core switch from each nexus then it means it will have to use the peer-link right since there is no second link to 2nd core ?

why wouldn't you use vpc in this design though its the best option as the po is logical then across the VSS and the Nexus switches given you full redundancy

[Network Pro]

what i am unclear about is, there is only 1 link going back to the core (no cross links) - how will vPC work from distrubution to core ? wont it have to traverse through the vPC peer-link which is not ideal right ? (vPC peer link is only used if there is a failure of cross link and not because by design there is only 1 link) - let me know if i have misunderstood this ?

6500-1 -----> N5k1

6500-2------->N5k2

NO CROSS LINKS BETWEEN 6500-2 and N5K1 and 6500-1 and N5K2

6500-1------VSS-------6500-2

|                                     |

|                                     |

N5k1------vPC---------N5k2

|                                    |

|-----------Server----------|

              (vPC)

[Mark Malone]

the 6500 is in VSS mode though its acting as one switch not 2 , the Nexus sees it as one logical unit

you would have a standard port-channel on VSS side , put 1 link in say t1/1/1 and the 2nd link in say t2/1/1 on the VSS side utilizing both switches using LACP then link each link back to the each 5k  and on the 5k side its vpc port-channel

yes your correct only in event of failure should peer-link carry traffic other than that its  , but with this setup traffic will be going out both links in the opo from the vss  to each 5k and not over the peer link if I have understood you correctly ,this is what im saying should look like physically below

[Network Pro]

not sure if i am making this clear (attached picture to make it clear)

so what i am trying to say, there are NO CROSS LINKS BETWEEN 6500-1 and N5K2 and 6500-2 and N5K1

1. THERE IS ONLY 1 LINK from 6500-1 -> N5K1 and 6500-2 -> N5K2 - will this still work? (attached picture)

2. will the server vPC work for the end server connected to both Nexus?

[Mark Malone]

1. THERE IS ONLY 1 LINK from 6500-1 -> N5K1 and 6500-2 -> N5K2 - will this still work? (attached picture)

Yes it wil still work , its up to you what way you place the links if you cross connect or not doesn't matter as the VSS is one unit split across both 5ks , 5ks and vss act as one unit each , you could add extra cross connects if you want to but you don't have 2 to get it to work , nexus is smart enough to know not to pass traffic across peer link unless theres an issue but you would be better with the 2 links each vss as thats the recommended way , what your doing is just what you would do say if you had a 3850 connected to it rather than a VSS pair

2 Server side cant be VPC it wont understand it , will work fine as LACP in normal PO and VPC on Nexus side , this is very standard setup have loads of servers running like that off the 5ks direct that need 10gb 1/1 ratio line rate so I don't put them in 2ks  

[Network Pro]

Thanks Mark clears up my first point. can I put all the 4 devices in 1 single port-channel/Vpc - will that work ?

regarding 2nd point - on the Nexus side i do vPC or normal PO for Servers, which is best practice ?

on the server side - is it usual teaming ? 

[Network Pro]

Hi Mark

any thoughts?

[Mark Malone · Accepted solution]

Hi port channel numbers are irrelevant apart from the nexus they need to be identical on each 5k but I would use different numbers for the pos on server and vss side for mgmt. purposes it will make it easier to troubleshoot rather than having everything same number throughout, so say on the nexus both switches have portchannel 150 going back to the VSS and on the VSS have standard PO 160 going back to the nexus switches and between the nexus switches and server do the same say 170 nexus side 180 server side

our servers we use VPC PO on the nexus side and on the server side the systems guys do nic teaming and load balancing on the operating system side of it , don't know too much about that but we use vpc  for sure, saying that should work both ways

[Network Pro]

This worked but i am still confused how the server with TEAMED on the server side but NOT on the switch end (no port-channel or vPC) works? shouldnt the N9k side (Switch) be vPC?

[Mark Malone]

It still works yes but you don't get the benefits of the VPC feature or algorithms it uses for forwarding traffic , that's why I was saying its better to use vpc but standard po will work too but less efficiently

"our servers we use VPC PO on the nexus side and on the server side the systems guys do nic teaming and load balancing on the operating system side of it , don't know too much about that but we use vpc  for sure, saying that should work both ways"