VDC (Virtual Device Context): 

• We can virtually divide a physical Nexus chassis in to multiple virtual chassis i.e. VDC.  

• Each VDC means a different switch (virtually). We can run all commands in each Switch (VDC) 

• We have to use cables between VDCs if we want to form trunk or any connection for transferring data because VDCs mean different switches 

  • Physically – It will appear as a loop if both VDCs are part of same physical chassis 

• Creation, Deletion, Modification of VDCs can be done from Default VDC only 

• By default – a physical complete chassis is known as Default VDC or Admin VDC 

• User should have VDC-admin privileges to do changes in respective VDC. To be able to operate all VDCs – user need to be Network-Admin role 

• Supervisor engine defines the no. of VDCs we can create in Nexus 7K Switch 

• For Sup1 – we can create 4 VDCs including “default vdc” 

• For Sup2 – Total of 5 VDCs can be created – out of which one will be default VDC 

• We move switchports in to other VDCs from Default VDC. So, if we move the port eth1/2 in to VDC 2 then eth1/2 administration will happen from VDC2 

• If we want to move the port eth1/2 back to Default VDC from VDC 2 – then this operation can only happen from “admin or default vdc” i.e. not from VDC2 

• User of VDC 4 cannot “view or operate” ports of VDC2 

• Control Plane i.e. CPU, memory is divided between each VDCs 

• Users of VDC2 will consider other VDCs as different switches, even though all are physically on same chassis 

   

• Remember that we can’t upgrade the IOS or Update License from “Non-default VDC” 

• If any global change is made – It will have impact on all VDCs. So “network-admin” should cautiously make changes 

• When we create VDC, then many things are shared such as CPU, RAM, MEMORY, Modules, Supervisor Engines, power supply, fabric modules, system tray, CMP and many more 

• VLAN information will not be shared between VDCs 

Create VDC: 

Delete VDC: 

• It is very dangerous as it will simply delete the virtual switch along with its configuration 

• Once we delete the VDC, all ports move to “default vdc or admin vdc” 

VDC information from default VDC: 

Saving Configuration: 

Switching VDCs: 

• Users of VDC1 will consider other VDCs as different switches, even though all are physically on same chassis 

• If we want to “move or switch” between VDCs (Ex, VDC 1 to VDC 3) 

  vdctest1#switchto vdc vdctest3 vdctest3 is name of VDC 3, we do not have to do Telnet or SSH or Console 

  vdctest3# Now we will be in vdctest3 

• In case we want to return to our own VDC (VDC 1) 

  vdctest3#switchback 

  vdctest1# now back to vdctest1 

• When we switched from VDC 1 to VDC 3, it does not tell you from which switch we’ve switched from, because we see only vdctest3# 

• To show the initial switch, we have to combine the names 

• We can do this on admin/default VDC 

• If VDC 1 is admin/default VDC 

  vdctest1#conf t 

  #vdc combined-hostname 

  #end 

   

  vdctest1#switchto vdc vdctest3 

  vdctest1-vdctest3# Now we will see both the names 

  Note: we cannot switch again to another vdc in here, only switchback 

Port-group: 

• Port-group depends upon the model 

• As each model has difference in grouping ports, it is advisable to refer cisco data sheet 

• Model Ex,  

  • M132XP-12L has grouping of 4 ports 

  • F132XP-15 has grouping of 2 ports 

   

• M series models does grouping of odd numbers and even number 

  • If we move port 3, then ports 1, 5, 7 will be moved 

  • If we move port 8, then ports 2, 4, 6 will be moved 

• F series models does grouping of 2 sequence numbers 

  • If we move port 3, then port 4 will be moved 

  • If we move port 17, then port 18 will be moved 

VDC Port Allocation: 

• when we move a port, It also moves the entire port-group. So missing ports will also be moved along with the port we want to move 

• So this port allocation has to be done very carefully. Ports may be having some servers connected. So, when we move, current configuration will be deleted and empty port will move along with members of port-group 

• Port-group depends upon the module model 

• M series models does grouping of odd numbers and even number 

  • If we move port 3, then ports 1, 5, 7 will be moved 

  • If we move port 8, then ports 2, 4, 6 will be moved 

• F series models does grouping of 2 sequence numbers 

  • If we move port 3, then port 4 will be moved 

  • If we move port 17, then port 18 will be moved 

Management (mgmt 0) in VDC: 

• Management 0 port i.e. mgmt0 is shared among VDCs. However, each VDC can have its own IP address on this interface 

  • mgmt0 in VDC 1 can have IP address 10.1.1.1/24 

  • mgm0 in VDC 2 can have IP address 10.1.1.2/24 

• mgmt0 is the only Single port on physical chassis, though it will appear as 4 ports in total (if 4 VDCs are present) 

• We can’t ping the Mgmt0 interfaces of other VDCs from one VDC if all are part of same Physical Nexus Switch 

  • Means mgmt0 (10.1.1.1/24- VDC 1) can’t ping mgmt0 (10.1.1.2/24- VDC2), Since both VDC1 & 2 are part of same physical Box 

• However, if different chassis being used then, ping will work provided correct network and subnet mask is used 

VDC HA: 

• HA Policy means High Availability policy 

• We have three options for single-sup HA 

  • Bringdown – Bring down the VDC 

  • Reload – Reload the supervisor 

  • Restart – Bring down the VDC, then bring the VDC back up 

• When we have only one supervisor engine (one sup) and if VDC gets corrupted / hung / stops working, we can set ha policy as RESTART 

• We can also set this policy to BRINGDOWN, but it will not serve any purpose because it will stop the operation for module. Restarting of module resolves many issues 

• Dual SUP HA Policy – We have three options for dual-sup HA 

  • Bringdown – Bring down the VDC 

  • Restart – Bring down the VDC, then bring the VDC back up 

  • Switchover – Switchover the supervisor 

• When we have two supervisor engine (two sup) and if VDC gets corrupted/hung/stops working, we can set dual-sup ha policy as SWITCHOVER 

• It will switch the management of VDC to backup supervisor engine. we can also change this policy but “switchover” is best and recommended for dual sup environment 

VDC resource limit: 

• To check the default resources allocated to VDCs 

  #show run To see full details about all the VDCs 

• To configure and limit the resources for a VLAN 

  #conf t 

  #vdc vdctest 

  #limit-resource vlan minimum 16 maximum 100 

  OR 

  #limit-resource vlan minimum 100 maximum equal-to-min 

  #end 

• We can configure and limit the resources for vrf, port-channel etc.