FEX Migration

I have been working extensively in the Data Center lately. I have a lot of respect and love for the Cisco Data Center technologies. In fact prior to just a couple of years ago, I had only worked on Catalyst systems. Unaware of the ISP/Carrier grade type of equipment that Cisco had to offer. After realizing this, I had a great desire to have a working knowledge and understanding of this technology. So our discussion today begins with FEX migrations with Cisco Nexus 2000 Series Fabric Extenders. This discussion is assumed you have some understanding of NX-OS.

Fabric Extenders in their simplest form are extensions to the Nexus 5K Series. They provide the 5Ks with greater port density. They are kind of like line cards for 6500s…

There are three different implementations for FEXs that you can choose from for your Data Center Design.

  1. Strait-through using static pinning: FEX is connected to a single Cisco Nexus switch. The single switch exclusively manages the ports on the FEX. Static pinning means that each downlink server port on the FEX is statically pinned to one of the uplinks between the FEX and the switch. Always uses same uplink. N5K
  2. Strait-through using dynamic pinning: FEX is connected to a single Cisco Nexus switch. The port between the FEX and the switch are bundled into a port channel and traffic is distributed across the uplinks that are based on the PortChannel hashing mechanism. N7K/N5K
  3. Active-active FEX using vPC: FEX is dual-homed to two Cisco Nexus Switches. vPC is used on the link between the FEX and the pair of switches. Traffic is forwarded between the FEX and the switches that are based on the vPC forwarding mechanisms. N5K

There are also several Cisco Nexus 2000 Series Fabric Extenders to choose from based on your design needs. Below are your choices.

  • Cisco Nexus 2148T GE Fabric Extender: Provides 48 fixed ports of Gigabit Ethernet interfaces for server connectivity and up to four 10 Gigabit Ethernet uplink interfaces in a compact one rack unit (1RU) form-factor
  • Cisco Nexus 2248TP 1GE Fabric Extender: Provides 48 Fast Ethernet and Gigabit Ethernet (100/1000BASE-T) server ports and four 10 Gigabit Ethernet uplink ports in a compact 1RU form factor
  • Cisco Nexus 2224TP 1GE Fabric Extender: Provides 24 Fast Ethernet and Gigabit Ethernet (100/1000BASE-T) server ports and two 10 Gigabit Ethernet uplink ports in a compact 1RU form factor
  • Cisco Nexus 2232PP 10GE Fabric Extender: Provides 32 Gigabit Ethernet and 10 Gigabit Ethernet (IEEE Data Center Bridging [DCB] and Fibre Channel over Ethernet [FCoE] capable) Enhanced Small Form-Factor Pluggable (SFP+) server ports and eight 10 Gigabit Ethernet (IEEE DCB and FCoE capable) SFP+ uplink ports in a compact 1RU form factor

You’ll want to be familiar with the features each model provides. For our discussion today we will be configuring a Cisco Nexus 2148T GE Fabric Extender. Our configuration that proceeds will be the same for any model of FEX however.

In this scenario I will be migrating two 2148T FEXs from their parent Nexus 5010s to a new Nexus 5548 parent device. The FEX is not connected to the 5548s at this point.

Provision the FEX for the 5548s

Execute the following commands to provision FEX number 101

N5548# config t
N5548(config)# slot 101 (This should resemble the number of your fex)
N5548(config-slot)# provision model N2K-CC248T (This should resemble the fex model number)
N5548(config-slot)# exit

Create a port-channel that will be used for Strait-through using dynamic pinning.

N5548(config)# int po1
N5548(config-if)# description FEX 101
N5548(config-if)# switchport mode fex-fabric
N5548(config-if)# fex associate 101

Configure FEX enabled interfaces and assign them to po1

N5548(config)#int eth1/5-6
N5548(config-if-range)# description FEX 101 E1/5
N5548(config-if-range)# switchport mode fex-fabric
N5548(config-if-range)# fex associate 101
N5548(config-if-range)# channel-group 1

At this point, the 5548s are aware of a provisioned FEX, I can start staging my FEX interface configurations. By doing this I am minimizing my down time of the when I perform my cut over for the hosts that are utilizing the FEX.

Show run will provide you with the interfaces of the FEX

CORE-N5548-PROD# sho run

interface Ethernet101/1/1
interface Ethernet101/1/2

Show fex 101 will not be recognized until the FEX is physically attached to the 5548s.

N5548# sho fex 101
FEX 101 not found

N5548(config)# int eth101/1/1
N5548(config-if)# switchport access vlan 14
N5548(config-if)# spanning-tree port type edge
N5548(config-if)# vpc orphan-port suspend
N5548(config-if)# channel-group 101 mode active

N5548(config)# int po101
N5548(config-if)# switchport mode access
N5548(config-if)# vpc 101

My configurations are complete, I will do the same for the second FEX. I can take the FEX uplinks from the 5010s and move them to the 5548s. The FEX will undergo a firmware update if you are moving to a new NX-OS version on the 5548. It will take roughly 8 minutes to update firmware.

Here is the output before migrating FEX 101, when connected to the 5010s

N5010# show fex 101 d

FEX: 101 Description: FEX101   state: Online
FEX version: 5.2(1)N1(3) [Switch version: 5.2(1)N1(3)]
FEX Interim version: 5.2(1)N1(3)
Switch Interim version: 5.2(1)N1(3)

Here is the output after migrating FEX 101, when connected to the 5548s

N5548# sho fex 101 detail

FEX: 101 Description: FEX0101   state: Online
FEX version: 7.0(6)N1(1) [Switch version: 7.0(6)N1(1)]
FEX Interim version: 7.0(6)N1(1)
Switch Interim version: 7.0(6)N1(1)
Extender Serial:
Extender Model: N2K-C2248TP-1GE,  Part No:
Card Id: 99, Mac Addr: 88:75:56:bf:60:42, Num Macs: 64
Module Sw Gen: 21  [Switch Sw Gen: 21]
post level: complete
Pinning-mode: static    Max-links: 1
Fabric port for control traffic: Eth1/5
FCoE Admin: false
FCoE Oper: true
FCoE FEX AA Configured: false
Fabric interface state:
    Po1 – Interface Up. State: Active
Eth1/5 – Interface Down. State: Configured
Eth1/6 – Interface Down. State: Configured
Fex Port        State  Fabric Port
11/02/2016 06:01:08.356480: Module register received
11/02/2016 06:01:08.357148: Image Version Mismatch
11/02/2016 06:01:08.357378: Registration response sent
11/02/2016 06:01:08.357560: Requesting satellite to download image
11/02/2016 06:07:13.672162: Image preload successful.
11/02/2016 06:07:14.787994: Deleting route to FEX
11/02/2016 06:07:14.802396: Module disconnected
11/02/2016 06:07:14.803518: Module Offline
11/02/2016 06:07:14.813590: Deleting route to FEX
11/02/2016 06:07:14.821427: Module disconnected
11/02/2016 06:07:14.845981: Offlining Module
11/02/2016 06:08:33.670509: Module register received
11/02/2016 06:08:33.671684: Registration response sent
11/02/2016 06:08:33.708916: create module inserted event.
11/02/2016 06:08:33.709560: Module Online Sequence
11/02/2016 06:08:39.951042: Module Online


Once the FEX completes it’s  firmware upgrade it will bring the provisioned interfaces online. At this point the migration is complete and the downstream hosts connected to the FEX should have network connectivity. You will want to repeat this process for each FEX. Be sure to configure the appropriate information like interfaces, fex number, and port channels.