vPC connectivity sanity check

[Jon Marshall]

Quick question as it has been a while so out of practice  

Can I connect a server with a vPC directly to a pair of Nexus C5548UP switches ie. don't need a FEX or anything in between ? 

Also any gotchas I need to be aware of ? 

Many thanks 

[MHM Cisco World · Accepted solution]

N5K run vPC and you use vPC VLAN to connect Server 
sure you can connect Server to both NSK, but make sure Server config port channel toward both NSK SW

[Jon Marshall]

Thanks for this. 

Reason I asked is in the configuration docs whenever you see diagrams with server connectivity it is always connecting to a pair of FEX that then connect to the 5K switches eg - 

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/layer2/b_Cisco_Nexus_5000_Series_NX-OS_/Cisco_Nexus_5000_Series_NX-OS__chapter8.html

so just want to be sure I do not need the FEXs. 

Jon

[MHM Cisco World]

We need FEX to increase number of port only in NSK.

[M02@rt37]

hello @Jon Marshall ,

you can connect directly! But, in best practice, we connect server (backend) on FEX or Nexus configured as LAN-ACCESS (Vpc Back to Back). We directly connect network equipement to Nexus Core, such as router, lan-access (nexus vpc back to back), firewall.

It's a question of design, not technical.

[Jon Marshall]

Okay, that's good to know thanks. 

Yes I understand the design aspect but we simply want to use a pair of 5548s as ToR switches (not as a core/distro pair) which is why I don't need FEXs in between. 

Jon

[M02@rt37]

@Jon Marshall , Then go straight forward to Nexus CORE

[Jon Marshall]

Could do but doesn't really work for us as we need the 10Gbps connectivity between a number of servers within the same cab and we would have to run cables back for all servers to core which is not what we want to do especially as this would burn through more ports. 

Plus we aren't using Nexus in the core so that complicates things for us. 

Happy with using them as ToRs, just wanted confirmation it would work which is much appreciated. 

Jon

[MHM Cisco World]

that why we use FEX,  it incease the port number of NSK that server can connect to. 
we can use two UPlink from FEX to NSK 
and use 18 or more port of FEX to connect server. 

[Jon Marshall]

Yes but as I said we don't have Nexus in the core so FEXs are not an option or if we did use them they would be in the same physical cab as the 5Ks which doesn't make a lot of sense  

Jon

[MHM Cisco World]

Core layer  is other Vendor 
Dis/access  layer  is NSK 5? that correct 

[Jon Marshall]

The N5Ks are simply being used as 10Gbps ToR access switches as we have some spare. 

Jon

[M02@rt37]

@Jon Marshall,

"Can I connect a server with a vPC directly to a pair of Nexus C5548UP switches ie. don't need a FEX or anything in between ? "

--- Yes! Your N5Ks are simply being used as 10Gbps ToR access switches, do not need FEX.

[MHM Cisco World]

that great use FEX and check below topology support for FEX/vPC/single/dual home
https://www.cisco.com/c/en/us/support/docs/switches/nexus-2000-series-fabric-extenders/200363-nexus-2000-fabric-extenders-supported-un.html

[M02@rt37]

@Jon Marshall ,

While vPC is not necessary in your specific case, it is a useful technology for scenarios where redundant connections and link aggregation are required. However, for your current requirement of connecting multiple servers within the same cabinet, a direct connection to the Nexus C5548UP switches should suffice.