Product Documentation

Configuring the Virtual MAC Address

Apr 30, 2013

The virtual MAC address is shared by the primary and secondary NetScaler Gateway appliances in a high availability setup.

In a high availability setup, the primary NetScaler Gateway owns all the floating IP addresses, such as the mapped IP address or the virtual IP address. It responds to address resolution protocol (ARP) requests for these IP addresses with its own MAC address. As a result, the ARP table of an external device (such as a router) is updated with the floating IP address and the primary NetScaler Gateway MAC address. When a failover occurs, the secondary NetScaler Gateway takes over as the new primary NetScaler Gateway. It then uses gratuitous address resolution protocol (GARP) to advertise the floating IP addresses that it acquired from the primary appliance. The MAC address, which the new primary appliance advertises, is that of its own interface.

Some devices do not accept GARP messages generated by NetScaler Gateway. As a result, some of the external devices retain the old IP-to-MAC mapping advertised by the old primary NetScaler Gateway. This situation can cause a site to become unavailable. To resolve the problem, you configure a virtual MAC address on both NetScaler Gateway appliances of a high availability pair. This configuration implies that both NetScaler Gateway appliances have identical MAC addresses. As a result, when failover occurs, the MAC address of the secondary NetScaler Gateway remains unchanged and ARP tables on the external devices do not need to be updated.

To create a virtual MAC address, create a virtual router identifier (ID) and bind it to an interface. In a high availability setup, the user needs to bind the ID to the interfaces on both the appliances.

When the virtual router ID is bound to an interface, the system generates a virtual MAC address with the virtual router ID as the last octet. An example of the generic virtual MAC address is 00:00:5e:00:01:<VRID>. For example, if you created a virtual router ID of value 60 and bind it to an interface, the resulting virtual MAC address is 00:00:5e:00:01:3c, where 3c is the hex representation of the virtual router ID. You can create 255 virtual router IDs ranging from 1 through 254.

You can configure virtual MAC addresses for IPv4 and IPv6.