Nexus - Config Sync

When you have two Nexus devices connected to each other via a VPC lpeer link, I have found it useful to have Config Sync enabled.  If you don't have config sync enabled, you will need to update each 5k separately and that is a pain at times. Additionally, if you make a change to one 5k and not the other, it will drop the connection. For example, you update the vlan associated with a switchport on Nexus5596_01, and not Nexus5596_02, it will down the port until Nexus5596_02 is updated. For this lab we are going to use Figure 1. Unfortunatley you cant simulate a switch in GNS3 so you will need to get your hands on some Nexus gear. 

Figure 1 - Nexus Lab

We will use the VPC Keep alive interface for this which is really cat6 cable connected between the switches on the mgmt interface on the back side.

Configurations:

Nexus5596_02# config t

Nexus5596_02(config)# configure sync
Nexus5596_02(config-sync)# switch-profile 5596 (This is what name you want to assigned to the profile)
Nexus5596_02(config-sync-sp)# sync-peers destination 192.168.1.1 (Peer device IP address)

Nexus5596_01# config t
Nexus5596_01(config)# configure sync
Nexus5596_01(config-sync)# switch-profile 5596
Nexus5596_01(config-sync-sp)# sync-peers destination 192.168.1.2

 Verifications:

 Nexus5596_02# show cfs peers

Physical Fabric
-------------------------------------------------------------------------
 Switch WWN              IP Address
-------------------------------------------------------------------------
 20:00:54:7f:ee:28:c3:00 192.168.1.2                             [Local]
                         Nexus5596_02
 20:00:54:7f:ee:25:08:80 192.168.1.1

Total number of entries = 2

Nexus5596_02#

Using the new feature: 

Nexus5596_02# config t

Enter configuration commands, one per line.  End with CNTL/Z.
Nexus5596_02(config)# configure sync
Nexus5596_02(config-sync)# switch-profile 5596
Switch-Profile started, Profile ID is 1
Nexus5596_02(config-sync-sp)# interface eth 101/1/12
Nexus5596_02(config-sync-sp-if)# switchport access vlan 100
Nexus5596_02(config-sync-sp-if)# verify (Optional)
Verification Successful
Nexus5596_02(config-sync-sp)# commit (Committing your changes to this device and the peer device)
Verification successful...
Proceeding to apply configuration. This might take a while depending on amount of configuration in buffer.
Please avoid other configuration changes during this time.
Commit Successful
Nexus5596_02(config-sync)# end
Nexus5596_02#

Nexus5596_01# show run int eth 101/1/12

!Command: show running-config interface Ethernet101/1/12
!Time: Fri Oct 19 04:30:13 2012

version 5.1(3)N1(1a)

interface Ethernet101/1/12
  switchport access vlan 100

Nexus5596_01#

Additional views:

If you don't want to commit your changes, they are stored on the switch untill you commit and you can view them.

Nexus5596_02(config)# config t

Nexus5596_02(config)# configure sync
Nexus5596_02(config-sync)# switch-profile 5596
Switch-Profile started, Profile ID is 1
Nexus5596_02(config-sync-sp)# interface ethernet 101/1/13
Nexus5596_02(config-sync-sp-if)# description example_of_not_commiting
Nexus5596_02(config-sync-sp-if)# end

Nexus5596_02# show switch-profile buffer

switch-profile  : 5596
----------------------------------------------------------
Seq-no  Command
----------------------------------------------------------
1       interface Ethernet101/1/13
1.1       description example_of_not_commiting

Further Reading:

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/system_management/502_n1_1/Cisco_n5k_system_mgmt_cg_rel_502_n1_1_chapter3.html