SonicOS 7 System

Subinterfaces

VLAN support on SonicOS is achieved by means of subinterfaces, which are logical interfaces nested beneath a physical interface. Every unique (tag) requires its own subinterface. For reasons of security and control, SonicOS does not participate in any VLAN trunking protocols, but instead requires that each VLAN that is to be supported be configured and assigned appropriate security characteristics.

VLAN IDs range from 0 – 4094, with these restrictions: VLAN 0 is reserved for QoS and VLAN 1 is reserved by some switches for native VLAN designation.

Dynamic VLAN Trunking protocols, such as VTP (VLAN Trunking Protocol) or GVRP (Generic VLAN Registration Protocol), should not be used on trunk links from other devices connected to the firewall.

Trunk links from VLAN capable switches are supported by declaring the relevant VLAN ID’s as a subinterface on the firewall, and configuring them in much the same way that a physical interface would be configured. In other words, only those VLANs that are defined as subinterfaces are handled by the firewall, the rest are discarded as uninteresting. This method also allows the parent physical interface on the firewall to which a trunk link is connected to operate as a conventional interface, providing support for any native (untagged) VLAN traffic that might also exist on the same link. Alternatively, the parent interface could remain in an ‘unassigned’ state.

VLAN subinterfaces have most of the capabilities and characteristics of a physical interface, including zone assignability, security services, GroupVPN, DHCP server, IP Helper, routing, and full NAT policy and Access Rule controls. Multicast support is excluded from VLAN subinterfaces at this time.

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