Chapter 6. Interfaces and Subnets

Table of Contents

6.1. Relationship between Interfaces and Physical Ports
6.1.1. Port groups
6.1.2. Interfaces
6.2. Defining an interface
6.2.1. Defining subnets
6.2.1.1. Source filtering
6.2.1.2. Using DHCP to configure a subnet
6.2.2. Setting up DHCP server parameters
6.2.2.1. Fixed/Static DHCP allocations
6.2.2.2. Restricted allocations
6.2.2.3. Special DHCP options
6.2.3. DHCP Relay Agent
6.3. Physical port settings
6.3.1. Setting duplex mode
6.3.2. Defining port LED functions

This chapter covers the setup of Ethernet interfaces and the definition of subnets that are present on those interfaces.

For information about other types of 'interfaces', refer to the following chapters :-

6.1. Relationship between Interfaces and Physical Ports

The FB6000 features two Gigabit Ethernet (1Gb/s) ports. These ports only work at gigabit speeds.

Each port features a green and amber LED, the functions of which can be chosen from a range of options indicating link speed and/or traffic activity.

The exact function of the ports is flexible, and controlled by the configuration of the FB6000.

6.1.1. Port groups

The FB6000 has two physical ports and no internal switch. This means that the port group configuration can either be the default where each port is in one group, or where both ports are in a trunked group

The port group has a trunk setting which defaults to being true. When there are two ports in the port group this is the only option. When only one port, it makes no difference. It is included for compatability with other models.

When using a trunked port group, the ports normally use and required LACP to a suitably configured switch. Only when the LACP confirms the correct config is the trunk set up. Until them the first active port is used on its own. If you do not wish to use LACP for the trunk (static config) you can edit the individual ethernet port settings to set lacp to false. If lacp mode is not set then it is assumed to be active for trunked ports, and passive for non trunked ports.

6.1.2. Interfaces

In the FB6000, an interface is a logical equivalent of a physical Ethernet interface adapter. Each interface normally exists in a distinct broadcast domain, and is associated with at most one port group.

Each port can operate simply as an interface with no VLANs, or can have one or more tagged VLANs which are treated as separate logical interfaces. Using VLAN tags and a VLAN capable switch you can effectively increase the number of physical ports.

If you are unfamiliar with VLANs or the concept of broadcast domains, Appendix C contains a brief overview.

By combining the FB6000 with a VLAN capable switch, using only a single physical connection between the switch and the FB6000, you can effectively expand the number of distinct physical interfaces, with the upper limit on number being determined by switch capabilities, or by inherent IEEE 802.1Q VLAN or FB6000 MAC address block size. An example of such a configuration is a multi-tenant serviced-office environment, where the FB6000 acts as an Internet access router for a number of tenants, firewalling between tenant networks, and maybe providing access to shared resources such as printers.