Networking

For a gateway router, the RV042 provides some useful addressing and routing functions to enable better network management. Those functions include support for multiple LAN subnets, non-subscription based dynamic DNS, one-to-one NAT, and basic distance vector routing protocols such as RIPv1 and RIPv2.

Multiple LAN Subnets

An easily overlooked feature on the RV042 is the ability to support multiple internal networks. Say you're running two subnets, one for your client PCs and the other for your servers. The RV042 allows assigning multiple addresses to the internal interface, providing a means of separating your network into different subnets. It's not as robust as 802.1q VLAN tagging, but does provide network separation and routing between subnets. If you're familiar with Cisco routers, this is akin to assigning a secondary IP address to an Interface.

In Figure 3, I've configured the RV042 to use 192.168.3.1 as its LAN IP address. Doing so makes the 192.168.3.0/24 subnet the network assigned by the DHCP server to the PCs on my LAN.

Figure 3: Configuring LAN subnets

I've also configured the RV042 to use 192.168.6.1 as its LAN IP address. I can then statically assign devices to the 192.168.6.0/24 network, using 192.168.6.1 as the gateway and DNS IP addresses.

I tested this by assigning a static IP address on the 192.168.6.0/24 network to a PC directly connected to the RV042. With this configuration, I could still surf the Internet, as well as access devices on the 192.168.3.0/24 network. The value here is this gives the network administrator additional options for segmenting a network.

Dynamic DNS

Remote access to a network requires either a static IP or URL. Most ISP services for homes and small offices have dynamic public IP addresses. A static IP can be expensive, though. In my area, Comcast charges $57.95 for a standard Internet service with a dynamic IP address. Comcast's business class Internet service that has the option of static IP addresses starts at $95 a month. If all you need is the static IP service, the additional $37/month is expensive.

The higher cost for a static IP address is due to the dwindling availability of public IP addresses using IPV4 addressing technology. There is a solution to this shortage, but it involves ISPs converting their networks to the newer addressing technology, known as IPV6. Japan, some European countries, and several Asia Pacific countries are rolling out IPV6 aggressively. The United States doesn't seem to be moving in this direction as quickly. 2008 will be interesting, though, with the Department of Defense having mandated that all its systems be migrated to IPV6 that year.

In the meantime, the simple solution is Dynamic DNS. The RV042 has configuration options for separate Dynamic DNS accounts on both WAN connections with three different organizations, including dyndns.org, 3322.org, and oray.net. As you can see from Figure 4, configuration is easy. Simply select your service and enter the user name, password, and domain you've set up with your chosen supplier.

Figure 4: Configuring Dynamic DNS

We've reviewed other routers where Dynamic DNS is a subscription-based service only. Kudos to Linksys for providing network administrators the option to use either a simple free account, or a more robust subscription-based service.

One-to-One NAT

The RV042 has multiple DMZ options to allow external access to internal devices, including designating one internal IP address as part of the DMZ, or assigning the additional WAN port as a physical DMZ port. I'll discuss the WAN/DMZ options shortly.

In the event your network has several servers with private IP addresses, and you want to allow external access, and have a range of public IP addresses, the One-to-One NAT function is a nice way to map those public IP addresses to those servers.

For example, let's say you have three servers, which you've assigned 192.168.3.2, 192.168.3.3, and 192.168.3.4 using the multiple subnet feature previously described. Let's also say you have three public IP addresses, 10.0.0.2, 10.0.0.3, and 10.0.0.4. (Of course, these are private IP addresses, but assume they're public IP addresses for purposes of this example.)

As you can see in Figure 5, I've configured the RV042 to translate the internal IP addresses 192.168.3.2-4 to 10.0.0.2-4. This allows the servers to be available on the internal LAN as well as available to external users targeting the 10.0.0.2-4 addresses.

Figure 5: One-to-One NAT setup

Routing Options

The RV042 can be configured either as a Gateway router, or as an internal network Router. The typical application is for the RV042 to be configured as a Gateway router, supporting your Internet connection(s) and providing NAT, firewall, and network services to your LAN.

In the event that you're using another router on your network to maintain access to the Internet and plan to use the RV042 to route between subnets, the RV042 can be configured as a basic Router. The RV042 supports both RIPv1 and RIPv2 routing protocols, as well as static routing to enable forwarding packets between subnets.

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