Citrix Netscaler L2 and L3 mode

Citrix NetScaler as an L2 Device

A NetScaler functioning as an L2 device is said to operate in L2 mode. In L2 mode, the NetScaler

forwards packets between network interfaces when all of the following conditions are met:

• The packets are destined to another device’s media access control (MAC) address.

• The destination MAC address is on a different network interface.

• The network interface is a member of the same virtual LAN (VLAN).

By default, all network interfaces are members of a pre-defined VLAN, VLAN 1. Address Resolution

Protocol (ARP) requests and responses are forwarded to all network interfaces that are members of

the same VLAN. To avoid bridging loops, L2 mode must be disabled if another L2 device is working

in parallel with the NetScaler.

Citrix NetScaler as a Packet Forwarding Device

A NetScaler can function as a packet forwarding device, and this mode of operation is called

L3 mode. With L3 mode enabled, the NetScaler forwards any received unicast packets that are

destined for an IP address that it does not have internally configured, if there is a route to the

destination. A NetScaler can also route packets between VLANs.

In both modes of operation, L2 and L3, a NetScaler generally drops packets that are in:

• Multicast frames

• Unknown protocol frames destined for a NetScaler’s

• Spanning Tree protocol (unless BridgeBPDUs is ON)

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