Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.


Fabric Extender question to a dual-homed N5k

According to latest release notes:

"Support for a maximum of 12 Fabric Extenders dual-homed to a vPC Cisco Nexus 5000 Series switch pair and a maximum of 576 hosts connected to Fabric Extenders connected to Cisco Nexus 5000 Series switches"

I have mixed mode so some of the FEX will only connect to one N5k despite the 2N5k will be vpc. Cisco calls this "Fabric extender straight-through topology". This is because I am running port-channel with VM on these particular FEX.

question is:

1. Can I assume 2148 is included per release notes?

2. Can I have more than 2 ports in the portchannels in straight-through mode?

3. Release notes show 576 host which is (12 max times 48 ports). I assume I can have more logical host meaning vm host via the port channels, right...?


New Member

Re: Fabric Extender question to a dual-homed N5k

Any Nexus 5000 can have a total of 12 FEX's connected to it physically.  If you have 12 FEX's in dual-homed mode, then that is the limit for both Nexus 5000's.  If you had 24 FEX's evenly distributed between the Nexus 5000's in straight-through mode, then that would be maximum in that configuration.  If you are mixing straight-through and dual-homed configurations, you would have to be within the 12 FEX per Nexus 5000 limit.

The 2148 is the first FEX, so yes it is the focus of the release notes.

The 2148 cannot have a local port-channel.  This is why you can only channel to a 2148 when using dual-homed (called Active-Active mode), one interface on each 2148, and it is tied together with a vPC configuration to make a port-channel.  The individual 2148's each only have one connection on them down to the server below.  The 2248 and 2232 do not have this restriction.

As of 4.2(1)N1(1), 576 refers to host interfaces.  If your host has virtual hosts, you just need to make sure you are within the limit of mac addresses in the system, which is 16,000 (13,800 unicast).


John Gill


configuration limits -