Nexus 7000 and 2000. Is FEX supported with vPC?

[jenny conlan]

I know this was not supported a few months ago, curious if anything has changed?

[Leo Laohoo]

Nexus 7K can become a parent for the 2K.  Just check the 2K Data Sheet to know the minimum NX-OS required.

[vdsudame]

Nothing has changed so far. Its still not supported.

Vinayak

[Steve Fuller · Accepted solution]

Hi Jenny,

I think the answer will depend on what you mean by is FEX supported with vPC?

When connecting a FEX to the Nexus 7000 you're able to run vPC from the Host Interfaces of a pair of FEX to an end system running IEEE 802.1AX (802.3ad) Link Aggregation. This is shown is illustration 7 of the diagram shown on the post Nexus 7000 Fex Supported/Not Supported Topologies.

What you're not able to do is run vPC on the FEX Network Interface that connect up to the Nexus 7000 i.e., dual-homing the FEX to two Nexus 7000. This is shown in illustrations 8 and 9 of under the FEX topologies not supported on the same page.

There's some discussion on this in the forum post DualHoming 2248TP-E to N7K that explains why it's not supported, but essentially it offers no additional resilience.

From that post:

The view is that when connecting FEX to the Nexus 7000, dual-homing does not add any level of resilience to the design. A server with dual NIC can attach to two FEX  so there is no need to connect the FEX to two parent switches. A server with only a single NIC can only attach to a single FEX, but given that FEX is supported by a fully redundant Nexus 7000 i.e., SE, fabrics, power, I/O modules etc., the availability is limited by the single FEX and so dual-homing does not increase availability.

Regards

[sam mackenzie]

Hi,

we enquired about this also with Cisco and basically were told that it is up for a future release but not the next release so it must not be ready. It exists for 5Ks.... There is defintely a requirement for anything which can't be dual-homed to two FEXs, the N7K isn't infallible and still prone to bugs

Cheers

Sam

[Raymond Kraft]

Hello,

I just wanted to update this topic that FEX dual-homing for N7K is now supported as of 7.2 code.

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/7_x/nx-os/release/notes/72_nx-os_release_note.html#pgfId-1125657

-Ray

[jenny conlan]

Hey Raymond,

 I reviewed the release notes and I don't see where it talks about dual-homing a FEX to two Nexus 7000, but perhaps I missed something...

[Raymond Kraft · Accepted solution]

Hi Jenny,

The section in the Release Notes mentioning this is a little vague, including below:

FEX AA features

Fabric Extender (FEX) is a pass-through/mux device designed to provide top of rack or end of line connectivity for servers/hosts. Currently FEX can be connected to only one Cisco Nexus 7000 series switch. If the switch goes down, FEX loses connectivity to the network. Hence all the singly connected hosts via the FEX also lose connectivity to the network. To solve this problem, FEX can be connected to two Cisco Nexus 7000 series switches in Active-Standby mode or Active-Active mode (vPC). We choose the Active-Active solution because vPC provides seamless switchover and faster convergence in case of switch failure. Moreover, traffic is also sprayed across both switches providing full utilization of bandwidth.

Please find the relevant Configuration Guide here with further details on this feature:

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus2000/sw/configuration/guide/b_Configuring_the_Cisco_Nexus_2000_Series_Fabric_Extender_rel_7_x/b_Configuring_the_Cisco_Nexus_2000_Series_Fabric_Extender_rel_7_x_chapter_010.html#concept_2A4...

I hope this helps!

-Ray

[jenny conlan]

Yes! That was buried in there - many thanks.