FEX VIFs limits based on # fabric interfaces

[NaelShahid_2]

Hi – I am trying to find some information on any limits on the number of FEX VIFs imposed by vntag and number of fabric interfaces between N2K and N7K… I know limits and rules exist with UCS 220X IOM and the fabric interconnect so I would assume (as using the same technology) limits exist in this scenario also.

[Amit Singh]

Yes, but we dont define the toal number of VIF's in this case when 2K connects back to N7K. The scalabiliy guide the total number of FEX and the FEX ports supported which would be equivalent to the total VIF's processed by the system on a particular hardware combination.

http://www.cisco.com/en/US/docs/switches/datacenter/sw/verified_scalability/b_Cisco_Nexus_7000_Series_NX-OS_Verified_Scalability_Guide.html#reference_E1ED6266546C444093CC27DEB0E1B38E

[NaelShahid_2]

Thanks for the response..

So looking at the scalability guide, with the latest NX-OS and sup2e 3072 server interfaces are supported, there is no mention of the number of fabric links. I assume if you had the minimum of 1 fabric uplink per FEX you could still have 3072 server interfaces?

With UCS IOM <> FI the number of vNICs supported is very much dependant on the number fabric uplinks connected….

[Amit Singh · Accepted solution]

Yes, you can have minimum 1 and maximum upto the supported uplinks. There are some design restrictions on N7k if you were to attached these to the parent line card. For example on an F1/F2 line cards all the uplinks have to be in the same SOC chip. But, yes, if you have the port counts to address this , you can have up to 3072 server ports.

UCS IOM is a different story as you are using FI's to manage the IOM/FEX and has limited hardware resources.

[NaelShahid_2]

with an f2e do we have the same restrictions where each FEX has to live on the same SOC? If we are connecting each FEX with only 1 uplink to an f2e, can we connected the 2nd FEX to the next port and the 3rd to next port etc etc? IE, we do not need each FEX to live on its own exclusive SOC and lose ports for connecting FEXs?

[Amit Singh]

Yes, you can have it that way where each FEX is using 1 port in one SOC. The only restriction is, Within each port-group (SoC), same ports must be used.

For example: FEX 100 is connected to SOC1 which manages E1/1-4. If you are connecting 1 link of FEX 100 on E1/1 and you wish to uplink another port in different port-group (say SOC2 which manages E1/5-8), You have to connect that to E1/5 ( port 1 of the SOC2).

Hope this clears the doubt and helps.

Cheers,

-amit singh

[NaelShahid_2]

Yes that helps, many thanks.

To summarize, I could have FEX1 > e1/1, FEX2 > e1/2, FEX3 > e1/3, FEX4 e1/4 (all ports in the SOC)… Each FEX with only the single uplink..