Here is another post regarding a topic from my new and upcoming CCNA Data Center course (200-155) at CBT Nuggets. This one talks about two specific Virtual Routing and Forwarding components called out in the exam objectives. Remember, a VRF is a logical separation at Layer 3 for routing information. You can liken it to a VLAN at Layer 2!
Cisco NX-OS devices have a default VRF and a management VRF. All Layer 3 interfaces exist in the default VRF until you assign them to another VRF. By default, all EXEC commands are processed in the default VRF unless you specify otherwise when you run a command.
Here is what you should know about the default VRF:
- Routing protocols are run in the default VRF context unless another VRF context is specified
- The default VRF uses the default routing context for all show commands.
- The default VRF is similar to the global routing table concept.
Here is what you should know about the management VRF:
- It is for management purposes only – duh!
- Only the mgmt0 interface can be in the management VRF; the mgmt0 interface cannot be assigned to another VRF.
- No routing protocols can run in the management VRF (static routing only).
You should also know the following VRF guidelines and limitations:
- When you make an interface a member of an existing VRF, NX-OS removes all Layer 3 configurations. Therefore, you should configure all Layer 3 parameters after adding an interface to a VRF.
- If you configure an interface for a VRF before the VRF exists, the interface is operationally down until you create the VRF.
- NX-OS creates the default and management VRFs by default. You should configure the mgmt0 IP address and other parameters after you add the mgmt0 interface to the management VRF.
- The write erase boot command does not remove the management VRF configurations. You must use the write erase command and then the write erase boot command.