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Introduction to Cisco NX-OS

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Jul 19, 2010.

Chapter Description

This chapter provides an introduction and overview of NX-OS and a comparison between traditional IOS and NX-OS configurations and terminology.

Virtual Device Contexts (VDCs)

The Nexus 7000 NX-OS software supports Virtual Device Contexts (VDCs), VDC(s) allow the partitioning of a single physical Nexus 7000 device into multiple logical devices. This logical separation provides the following benefits:

  • Administrative and management separation
  • Change and failure domain isolation from other VDCs
  • Address, VLAN, VRF, and vPC isolation

Each VDC appears as a unique device and allows for separate Roles-Based Access Control Management (RBAC) per VDC. This enables VDCs to be administered by different administrators while still maintaining a rich, granular RBAC capability. With this functionalit, each administrator can define virtual routing and forwarding instance (VRF) names and VLAN IDs independent of those used in other VDCs safely with the knowledge that VDCs maintain their own unique software processes, configuration, and data-plane forwarding tables.

Each VDC also maintains an individual high-availability (HA) policy that defines the action that the system will take when a failure occurs within a VDC. Depending on the hardware configuration of the system, there are various actions that can be performed. In a single supervisor system, the VDC can be shut down, restarted, or the supervisor can be reloaded. In a redundant supervisor configuration, the VDC can be shut down, restarted, or a supervisor switchover can be initiated.

There are components that are shared between VDC(s), which include the following:

  • A single instance of the kernel which supports all of the processes and VDCs.
  • Supervisor modules
  • Fabric modules
  • Power supplies
  • Fan trays
  • System fan trays
  • CMP
  • CoPP
  • Hardware SPAN resources

Figure 1-5 shows the logical segmentation with VDCs on the Nexus 7000. A common use case is horizontal consolidation to reduce the quantity of physical switches at the data center aggregation layer. In Figure 1-5, there are two physical Nexus 7000 chassis; the logical VDC layout is also shown.

Figure 1-5

Figure 1-5 Logical Segmentation with VDCs on the Nexus 7000

VDC Configuration

This section shows the required steps to creating a VDC; once the VDC is created, you will assign resources to the VDC. VDC(s) are always created from the default admin VDC context, VDC context 1.

Example 1-11 shows how to configure the VDC core on Egypt.

Example 1-11. Creating VDC "core" on Egypt

egypt(config)# vdc core
Note:  Creating VDC, one moment please ...
egypt# show vdc
vdc_id  vdc_name                          state               mac
------  --------                          -----               ----------
1       egypt                             active         00:1b:54:c2:38:c1
2       core                               active        00:1b:54:c2:38:c2

egypt# show vdc core detail
vdc id: 2
vdc name: core
vdc state: active
vdc mac address: 00:1b:54:c2:38:c2
vdc ha policy: RESTART
vdc dual-sup ha policy: SWITCHOVER
vdc boot Order: 2
vdc create time: Mon Feb 22 13:11:59 2010
vdc reload count: 1
vdc restart count: 0

Once the VDC is created, you now have to assign physical interfaces to the VDC. Depending on the Ethernet modules installed in the switch, interface allocation is supported as follows:

The 32-port 10-Gigabit Ethernet Module (N7K-M132XP-12), interfaces can be allocated on a per port-group basis; there are eight port-groups. For example, port-group 1 are interfaces e1, e3, e5, e7; port-group 2 are interfaces e2, e4, e6, e8.

The 48-port 10/100/1000 I/O Module (N7K-M148GT-11) can be allocated on a per-port basis.

The 48-port 1000BaseX I/O Module (N7K-M148GS-11) can be allocated on a per-port basis.

A future module, N7K-D132XP-15, interfaces will be allocated per 2 ports per VDC.

Example 1-12 demonstrates how to allocate interfaces to a VDC.

Example 1-12. Allocating Interfaces to a VDC

egypt(config)# vdc core
eqypt(config-vdc)# allocate interface Ethernet1/17
egypt(config-vdc)# allocate interface Ethernet1/18

To verify the interfaces allocation, enter the show vdc membership command as demonstrated in Example 1-13.

Example 1-13. Verifying Interface Allocation to a VDC

egypt(config-vdc)# show vdc membership

vdc_id: 1 vdc_name: egypt interfaces:
        Ethernet1/26          Ethernet1/28          Ethernet1/30
        Ethernet1/32          Ethernet2/2           Ethernet2/4
        Ethernet2/6           Ethernet2/8           Ethernet2/26
        Ethernet2/28          Ethernet2/30          Ethernet2/32
        Ethernet3/4           Ethernet3/5           Ethernet3/6
        Ethernet3/7           Ethernet3/8           Ethernet3/9
        Ethernet3/11          Ethernet3/12          Ethernet3/13
        Ethernet3/14          Ethernet3/15          Ethernet3/16
        Ethernet3/17          Ethernet3/18          Ethernet3/19
        Ethernet3/20          Ethernet3/21          Ethernet3/22
        Ethernet3/23          Ethernet3/24          Ethernet3/25
        Ethernet3/26          Ethernet3/27          Ethernet3/28
        Ethernet3/29          Ethernet3/30          Ethernet3/31
        Ethernet3/32          Ethernet3/33          Ethernet3/34
        Ethernet3/35          Ethernet3/36          Ethernet3/39
        Ethernet3/40          Ethernet3/41          Ethernet3/42
        Ethernet3/43          Ethernet3/44          Ethernet3/45
        Ethernet3/46          Ethernet3/47          Ethernet3/48

vdc_id: 2 vdc_name: core interfaces:
        Ethernet1/17          Ethernet1/18          Ethernet1/19
        Ethernet1/20          Ethernet1/21          Ethernet1/22
        Ethernet1/23          Ethernet1/24          Ethernet1/25
        Ethernet1/27          Ethernet1/29          Ethernet1/31
        Ethernet2/17          Ethernet2/18          Ethernet2/19
        Ethernet2/20          Ethernet2/21          Ethernet2/22
        Ethernet2/23          Ethernet2/24          Ethernet2/25
        Ethernet2/27          Ethernet2/29          Ethernet2/31
        Ethernet3/1           Ethernet3/2           Ethernet3/3

In addition to interfaces, other physical resources can be allocated to an individual VDC, including IPv4 route memory, IPv6 route memory, port-channels, and SPAN sessions. Configuring these values prevents a single VDC from monopolizing system resources. Example 1-14 demonstrates how to accomplish this.

Example 1-14. Allocating System Resources

egypt(config)# vdc core
egypt(config-vdc)# limit-resource port-channel minimum 32 maximum equal-to-min
egypt(config-vdc)# limit-resource u4route-mem minimum 32 maximum equal-to-min
egypt(config-vdc)# limit-resource u6route-mem minimum 32 maximum equal-to-min
egypt(config-vdc)# limit-resource vlan minimum 32 maximum equal-to-min
egypt(config-vdc)# limit-resource vrf minimum 32 maximum equal-to-min

Defining the VDC HA policy is also done within the VDC configuration sub-mode. Use the ha-policy command to define the HA policy for a VDC as demonstrated in Example 1-15.

Example 1-15. Changing the HA Policy for a VDC

egypt(config)# vdc core
eqypt(config-vdc)# ha-policy dual-sup bringdown

The HA policy will depend based on the use-case or VDC role. For example, if you have dual-supervisor modules in the Nexus 7000 chassis or if the VDC role is development/test, the VDC HA policy may be to just shut down the VDC. If the VDC role is for the core and aggregation use case the HA policy would be switchover.

6. Troubleshooting | Next Section Previous Section

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