Monthly Archives: February 2012

Cisco Nexus 7000 OTV configuration

Another post, this time about the basic OTV configuration on a Nexus 7000.
The OTV configuration has the be made on a different switch (or VDC) where no SVI’s are configured for the VLAN’s you want to extend to the other site.
First of all some terminology:
  • Edge device: This device performs layer 2 activities (to the internal network) and OTV transportation to the other site(s).
  • Transport network: This is the network (can be layer 3) that connects all the sites. This is your WAN connection, possible managed by your service provider.
  • Join interface: This is the uplink interface on the edge device that is connected to the transport network.
  • Internal interface: This is the interface on the edge device that is connected to the internal network.
  • Overlay interface: This is a logical interface, with support for multi access, multicast. This interface encapsulates layer 2 frames in IP headers (also ‘MAC routing’)
  • Overlay network: A logical network that connects all sites together and uses MAC routing for interconnecting the sites.
  • Site: Your (layer 2) network on a location. In most cases, this is one of your datacenters.

Nexus 2248TP FEX connected to a Nexus 7000: part 1 basic connection

Cisco published a configuration guide for connecting a Nexus 2248TP FEX to a Nexus 7000. I’ll explain the configuration process to configure the FEX for basic connectivity.

A FEX is a Nexus 2000 series switch. In a very high level explanation, this switch is a switchport module in a separate 1U chassis, which is configured and controlled from a Nexus 5000/7000. There is 1 drawback: the switchports on the FEX can only be used for host ports. It’s not possible to connect other switches to a FEX port because of the fact that BPDUguard is enabled by default. It’s not possible to disable BPDUguard. Switchports on the FEX can be used for layer 2 and layer 3 connections. For more information about the FEX itself I’ll refer to this link

All configuration is done on the Nexus 7000 with NX-OS 6.0(1). In this scenario, the 2248TP FEX is connected to switchport ethernet 1/1  (10GE port) of the Nexus 7000 with a twinax cable.

First, let’s configure a switchport for the FEX:
switch(config)# int ethernet 1/1
switch(config-if)# switchport mode fex-fabric
Error: feature-set fex is not enabled
Okay, we have to install (!) and enable the fex feature before we can continue
switch(config)# install feature-set fex
switch(config)# feature-set fex
And try again to configure the fex-fabric mode: