Specifications

The router we chose was a MultiTech RF500S. It meets our requirements and technical support from

Multitech has been outstanding.

8.1 WAN Interface

DSL service providers offer three types of modems, External with an Ethernet port, External with USB port

and Internal PCI. There are pros and cons to each. An external Ethernet modem is the most flexible because

it can be connected directly to a computer or used with a router to create a LAN. We used an external DSL

modem for both Vitts and Verizon DSL.

The customer interface of the Verizon Westell ADSL modem is 10baseT Ethernet. This connects directly

to the Wide Area Network (WAN) port of the router. Verizon uses PPPoE encapsulation. This requires the

user to log in, much the same as with a dialup account. The router implements PPPoE eliminating the need

to run special software on the PCs. With PPPoE the WAN IP address, Gateway address and DNS address

are configured automatically each time the router logs in.

If the DSL connection is idle for a while Verizon will automatically disconnect. The router maintains a

keep alive that prevents the connection from being dropped. This simulates a true always on connection.

The router uses the keep alive to verify the Internet is accessible. If the connection is lost the router

automatically attempts to reconnect. If the connection is down for more then a three minutes and one of the

devices on the LAN is requesting Internet access the router activates the back POTS dialup modem. The

router continuously attempts to reestablish the DSL connection. When that occurs it disconnects the POTS

modem and routes traffic though the high-speed connection. Except for momentary outages and difference

in speed this is invisible to the user.

8.2 Automatic Fail over

When a client on the LAN requests Internet access the router verifies the DSL connection is working. This

is the preferred Internet connection. If DSL is down the router automatically uses the analog modem to

connect to the dialup ISP. The router includes an idle timer to disconnect the analog modem after a period

of inactivity. This prevents the modem from tying up the dialup connection unnecessarily. The router

continuously attempts to reestablish the broadband connection. When DSL service is restored dialup is

automatically terminated.

This feature turned out to be very useful. The router was set up before we had DSL. This allowed us to test

and debug the dialup configuration prior to getting DSL After our first DSL provider went out of business

we were forced to use dialup full time. When the Verizon account was activated we simply plugged in the

Westell modem and entered our PPPoE account information into the router. Once again we were up and

running on DSL.

Setting up the dialup account is similar to Windows dialup networking; it requires POP phone number, user

name, and password. With PPP the WAN IP address, Gateway address and DNS address are configured

automatically each time the router logs in. These setting are different depending on if the connection is

dialup or DSL. The router hides the difference from network clients.

Both Vitts and Verizon service has been reliable. We have never lost DSLAM sync. All outages have been

either DNS or ISP internal routing problems. The few outages that occur last a few minutes to at most

several hours. That fact that problems have been with the service provider’s internal network operation

validates our choice to obtain backup dialup from a different vendor.