SmallNetBuilder

Interfaces

Of the USG100’s seven Gigabit interfaces, the first two ports are designated as WAN interfaces and the other five separate internal traffic into various LANs. Even though the WAN ports will likely be connected at far lower speeds than 1000 Mbps, it is encouraging to have this level of functionality in all ports on a router. MTU is adjustable by interface, but only from 576-1500 bytes; jumbo frames are not an option.

The default configuration has Ports 1 and 2 designated for WAN connections, Ports 3 and 4 for LAN1, Port 5 is for LAN2, Port 6 for a wireless LAN intended to connect to an Access Point, and Port 7 for the DMZ. Ports 3-7 can be reconfigured to any of these four designations, though, as shown in Figure 5 below.

Figure 5: Port Assignment

As you can see in the status screen in Figure 6, there are different subnets for the LAN1, LAN2, WLAN, and DMZ interfaces. The value in running different subnets for each of the LANs is the ability to control traffic between each of your networks using Firewall rules which can be applied by interface, IP, or subnet.

Figure 6: Interfaces

In addition to the seven gigabit Ethernet interfaces, the PCMCIA slot on the back of the USG100 will support a 3G WWAN card or an 802.11b/g WLAN card. Further, a 3G USB WWAN device can be connected to one of the two USB ports on the front of the USG100.

VLANs

Dividing a network into multiple subnets effectively provides the value of VLAN broadcast control without using expensive managed switches. With the above configuration on my test USG100, a PC connected to an unmanaged switch off the LAN1 interface received an IP in the 192.168.21.0/24 subnet, while a  PC connected to another unmanaged switch off the DMZ interface received an IP in the 192.168.13.0/24 subnet.

Further, multiple VLANs can be configured on a single USG100 interface, allowing the USG100 to be connected to a managed switch that supports 802.1q VLANs. The USG100 can then be configured with different DHCP servers per VLAN, enabling 1-1 subnet to VLAN network mapping.

I tested this functionality by configuring two different VLANs on the LAN1 interface of the USG100 with separate DHCP servers for each VLAN as listed in Figure 7 below. I then configured a Netgear GS716T managed switch with the same VLANs, and assigned the new VLANs to two different ports on the switch.

Figure 7: VLANs

There were a few more configurations applied in the GS716T. But the end result was I could plug a PC into the appropriate ports of the GS716T and get an IP addresses corresponding to the VLAN assignments in the USG100, validating the USG100's recognition of 802.1q VLAN tags.

Routing

Configurable routing options include Policy Routes, Static Routes, RIP and OSPF. Policy Routes are the workhorse for controlling traffic through the USG100. The Policy Route option in the USG100 allows for defining traffic paths based on incoming interface, source and destination subnets, service (protocol), and a next-hop destinations such as an interface or IP.

In Figure 8, I've configured the top Policy Route to route traffic to a subnet behind another router. The traffic being routed is originating on the LAN2_SUBNET (192.168.3.0/24) and going to a subnet behind another router, defined by an object I created called DFLLAN (192.168.10.0/24). The next-hop for this traffic is the IP address of the other router, which I created in an object called DFL.

Figure 8: Policy Routes

The second Policy Route shown in Figure 8 is to route traffic over the VPN tunnel. This configuration specifies that traffic originating from my internal subnet (LAN2_SUBNET) going to a remote subnet (ZLAN) accessible over the VPN tunnel is reachable via an object called ZVNTest, which specifies the IP address at the other end of my VPN tunnel.