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Hands-on hardware: DSL / cable modem routers

by Steve Antonoff

December 11, 2000 —

 

You've got your DSL connection. You're using an ISP-provided DSL bridge (aka DSL
modem). Your LAN is routed through one computer that accesses the Internet with network
address translation (NAT) or proxy services. Your service is OK, but you feel there are
definitely some weak spots.

Where are the weaknesses?

The most obvious weakness is that Internet access depends on one computer. If that
computer is a server, it's probably up and running most of the time; but then you-know-
what happens, maintenance is required, and so on. And, of course, such things will
happen at the worst possible moment for someone on the network.

Another weakness is that the computer serving as the router/NAT runs at least four
pieces of software that consume resources: DHCP, NAT/Proxy, the Point to Point Protocol
Over Ethernet (PPPoE) service, and the DSL connection software. All are OK, but
consume valuable resources.

Also, your DSL probably goes down more often than you'd like. When this happens,
the software establishing the connection to the DSL must continually retry the
connection -- or, more likely, try a few times, then give up until an administrator
instructs it to try again. We were offline for 6-8 hours last week because no one
restarted the DSL connection. The actual outage was probably much shorter.

Where do you go for improvements? For a minimal investment ($80-$150, depending on
brand), you can add a DSL/cable modem router, a semi-intelligent box that sits between
the DSL bridge and the LAN. A router is smart enough to continually retry the DSL
connection after it goes down. It can also provide some valuable services to your LAN
and lighten your server's workload.

Thanks to several vendors, I was able to try three different routers: a Hawking
Technology PN9225 10/100 Broadband DSL/Cable Router, a Trendware TW100-W1CA, and a
Linksys BFSR11.




Feature Comparison:
Three DSL/Cable Modem Routers
  Hawking
PN9225		 TrendWare
TW100-W1AC		 Linksys
BEFSR11
Default IP 192.168.10.10 192.168.0.1 192.168.1.1
Switchable Xover No No Yes
Reset button Yes No Yes
DHCP 253/Fixed &
Dynamic		 128/Dynamic 253/Dynamic
DNS No No No
PAT 10 TCP/4 UDP Unspecified 10
DMZ support Yes No Yes
Serial Port No Yes No
Telnet Yes Yes (port 333) No
Browser Yes No Yes
Dedicated GUI Yes Yes Yes
Configuration Use browser Use GUI Use browser

Each of those devices connects in the same way: a category 5 network cable goes from
the DSL bridge to the router, and another cable goes from the router to the hub or
switch. As with other devices of this nature, you sometimes need a crossover cable,
sometimes a straight-through variety. Some setup is required for each, and depending
on the capabilities you choose to use, some networking skills may be handy. The Linksys
has a nice feature: a switch that changes the LAN port from MDI to MDIX, so you can use
either type of cable.

All three devices allow you to do configuration over an IP-based network, and each
comes configured with a default IP address. None of the devices was hard to set up. A
little knowledge of your network can make this a lot easier.

The table below lists the products' features and differences; at the end of the
column, I include some notes on setting up the PN9225.

While all three devices are probably adequate for home use, the Hawking Technology
PN9225 has some advantages for the small business or remote office. The Trendware
router, though, had some serious shortcomings. I've summarized those below the
features table.

The important differences between the boxes are the way they handle port address
translation (PAT) for incoming traffic, the inclusion of a demilitarized
zone (DMZ), and the completeness of the DHCP.

Of the three, only Hawking allows DHCP reservations -- an address assigned to a
network adapter based on its permanent MAC address. This allows servers, for example,
to use DHCP to get their addresses without the address bouncing around. In my network,
I set up reservations for all permanent, resident PCs. In this case, DHCP is used to
change the configuration when necessary and to document each computer's IP address.
Transient PC's get an address from the pool of unassigned addresses.

For incoming traffic, all three devices provide some form of rerouting based on IP
port number. The Linksys and the Trendware, however, force the connection to the
internal computer to use the same port number as the incoming request. Hawking allows
the internal port to differ from the original. For example, if you have two machines
behind the router that provide WWW service, both use port 80. You can tell the Hawking
to reroute port 80 requests to one machine, using port 80, while requests on port 81
can be routed to the other machine but mapped to port 80. The same holds true for
Telnet, FTP, etc.

Finally, if you use one computer for lots of stuff, it might be helpful to just open
it up to any port request that it will process. Example: You have one machine that
does FTP, HTTP, Telnet, POP3, and SMTP for employees connecting over the Internet.
Rather than program every required port into the PAT table, set the machine up as the
DMZ machine; all requests to ports not translated by PAT will be sent to the
DMZ computer.

I would like to see a DNS service for the internal network, but none of these
devices provide it. You'll need to either put HOSTS tables on all the computers for
naming of the internal network or run WINS or DNS on a server. I'm keeping my DNS and
WINS on the prime server.

Conclusion

If you have DSL or cable modem service, these devices are worth the small investment.
I'd stay away from the Trendware, at least until they fix the problems I have
described. The street prices for the Hawking Technology and Linksys boxes are
similar.

Example of setting up the PN9225

The PN9225 has both a Telnet and a Web interface to do its setup. It comes with a
default IP address of 192.168.10.10 and a netmask of 255.255.255.0. After the cables
are connected, you will need to add an address in the 192.168.10.x range to a computer
on the network, to let it talk to the PN9225. I chose 192.168.10.1. Any address from
1 to 254, except 10, will work as the last octet. I started up Internet Explorer and
asked it to go to 192.168.10.10; voila, an authentication screen appeared. Using the
default user ID and password got me into the configuration pages. I used the wizard to
do the initial setup, then explored the Advanced Setup pages. Once the configuration
was done, Internet connectivity was established. It has been much more stable than
without the router: outage recoveries are automatic and IP address changes are
invisible.

Problems encountered with the Trendware W1CA


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