Alcatel-Lucent OmniSwitch Virtual-Chassis Back-to-Back / VC-B2B Configuration

Target of the „Alcatel-Lucent OmniSwitch Virtual-Chassis Back-to-Back“ (VC-B2B) is to be a modern alternative to the often deployed „Multi-Chassis Back-to-Back“ (MC-B2B) design. The use of the Virtual-Chassis technology reduces the amount of managed nodes in the network while preserving the high-availability aspect of the solution.

One of the main advantages of the Virtual-Chassis is, that it supports IPv6 (which wasn't available with MC-B2B before).

To enable a seamless migration of virtual machines (VMs) across the DCs (e.g. vMotion), it is necessary to maintain the Gateway (IP-Address, virtual MAC-Address) in a identical fashion. This is being achieved by leveraging VRRP (Virtual Router Redundancy Protocol), which allows to deploy virtual gateways.

To enable the same virtual gateway in both Data Centers, which allows the shortest path towards campus network, we prevent VRRP-Advertisements on the DC-Interconnect! (Running in a „Master / Master“-fashion instead of a „Master / Standby“)

The following ACL snapshot shows that the DC-Interconnect is configured on Chassis 1, Slot 2, Port 1-2 and Chassis 2, Slot 2, Port 1-2. The „Destination-MAC-Address“ is the virtual Multicast-MAC that is being used by VRRP for advertisements. (This policy/ACL avoids that we need to create many more specific policies. Please ensure that this is applied on both VCs!)

policy port group to-other-dc 1/2/1-2 2/2/1-2  
policy condition drop-vrrp source port group to-other-dc destination mac 01:00:5E:00:00:12 
policy action drop disposition drop 
policy rule drop-vrrp-adv condition drop-vrrp action drop 
qos apply

Create „physical“ IP-Interfaces, those need to be unique across DCs.

! IP:
ip interface "vlan-10" address mask vlan 10 ifindex 1
ip interface "vlan-20" address mask vlan 20 ifindex 2

You can only create a VRRP-Interface once an IP-Interface has been created!

The following commands will create the same gateway (*.254) on both Virtual-Chassis.

ip load vrrp
vrrp 10 10 priority 100 preempt interval 1
vrrp 10 10 address
vrrp 20 20 priority 100 preempt interval 1
vrrp 20 20 address

Servers/VMs can now seamlessly move across DCs while preserving their shortest path towards the campus network.

We strongly suggest to create a „Out-of-Band“ network for each of the VCs and connect the EMP-Ports in that network/VLAN. If you connect more than one Virtual-Chassis in the same VLAN, make sure to configure the „Virtual-Chassis-Group“ to a unique value.


  • OmniSwitch 6900 (OS6900) needs „Advanced Routing“-License (otherwise there is no Virtual-Chassis capability)
  • OmniSwitch 10K (OS10K) needs „Advanced“-License (otherwise there is no Virtual-Chassis capability)
english/omniswitch_virtual_chassis_back-to-back_vc-b2b.txt · Zuletzt geändert: 2014/07/23 20:05 von benny

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